Romance in the world’s most wired city.
A couple posing for a selfie with hot pink flowers
Seoul mates: for lovers, each day is a milestone—especially the day they began using the app Between to store digital keepsakes.

Among twenty-five million, they were two, speeding toward the glowing span of the Wonhyo Bridge on a warm spring night, the scooter trailing pink balloons. They were born in Seoul in 1985 and 1992. They were natives of the most wired city in the world, a megalopolis that is nearly twice as dense as New York but maintains the wide margins of the suburbs—roomy restaurants, boulevards lined with trees. The city belonged to them, beaming its vital signs at speeds of more than fifty megabits per second to its citizens, who bunched and flowed in near-instantaneous reply. Their smartphones were lanterns, illuminating the urban grid. Bubbles within windows within browsers within screens: it was as though, through some mathematical trick, the smaller the interface the more freedom it afforded.

It was May. Jimin, a computer engineer with serious eyes and a square jaw, was finishing up his degree at Seoul National University, having taken off several years to perform military service. He had been a detection analyst, interpreting intelligence signals. Jiyeon (Yundi), a sophomore, had a heart-shaped face and a chic, whimsical way of dressing: that night, she was wearing a floral do-rag in her long black hair. They had first met in February, on a student ski trip to Phoenix Park Ski World. Jimin was staying with nine boys. Yundi was staying with seven girls. The boys’ room had called the girls’ room on the hotel phone—since they were strangers, this was the only way to communicate; the boys had got a list of girls’-room numbers from the trip’s chaperones—and asked if they wanted to do a bangting (“room-meeting”), a type of group blind date. The gathering, in Room 206, had been raucous, not a moment to get to know someone. Jimin and Yundi remembered having exchanged a high five.

Three months later, the university held a spring fair. Students bounced on trampolines and belted out songs to a karaoke machine. Jimin and some friends were sitting on the grass, eating scallion chicken and drinking a sweet rice wine called makoli. Yundi walked by, and Jimin invited her to join them. Eventually, he asked her to pass him some chicken. When she handed him the plate, he complained, teasingly, that she’d given him only scallions. They’d have to eat chicken together sometime, he said. She told her friends afterward, “He’s twenty-nine, but he’s so cute!”

Yundi took the subway home from the festival. As she sat on the train, debating whether it would seem too forward to friend Jimin on Facebook, her phone—a Samsung Galaxy in a pearlescent case—dinged, and a push notification appeared, announcing that Jimin wanted to be her friend.

Within weeks, Jimin and Yundi were wildly in love. One afternoon, Jimin attended an event at which someone was handing out balloons. He tied them to the back of his motorbike, thinking it would look like a newlyweds’ car, and picked Yundi up after her classes. From campus, they headed north, passing rail yards and fish markets; apartment buildings filled with housewives snapping up the online-auction bargains of the day (bags of oranges, puffy jackets, belly-button-lint removers); clothing stores packed with customers pouting in front of mirrors, as they posed for chakshot, pictures of themselves trying on outfits, which they sent to their friends, who would message back with a yes or a no; soju bars; cram schools; PC bangs, the smoke-filled, twenty-four-hour gaming centers that were quickly becoming futuristic anachronisms, populated by dwindling numbers of adolescent boys slurping instant noodles in front of humming terminals. (Now that the Internet was so fast at home, no one needed to go to bangs to compete in multi-player games.)

Yundi held on tight to Jimin. Beneath them, in the subways, the 4G LTE network provided cellular service, even though no one talked on the phone or sent texts anymore, preferring to chat on the mobile-messaging app KakaoTalk. The WiMax connection was fast enough to stream music videos. Passengers watched live television, via DMB, and read comic books, the best of which were now available exclusively through the Internet search providers who commissioned them. Trains arrived every ninety seconds, announced by piped-in birdsong. On the platforms were kiosks with forty-six-inch touchscreens. They showed movie trailers, monitored exchange rates, dispensed coupons, and made restaurant recommendations. Nearby, a resident could order groceries from a virtual supermarket by scanning QR codes that corresponded to the desired items, which would be delivered to his house in a matter of hours. A commuter who needed to connect to a bus could check the availability—not on a bus schedule but on a digital map that charted buses in real time. Even though millions of people rode buses, you hardly ever saw crowds waiting at a bus stop.

The technologies seemed to trigger urges in addition to transmitting them, as though the city’s inhabitants and its machines had merged into a single nervous system, dendrites intermingling with optical fibres. A stranger once thrust his smartphone into a pretty woman’s hand and ran off, hoping that she would feel obliged to track him down in order to return it.

The joyride ended at Han River Park, which encircles Seoul’s main financial district. Jimin and Yundi spread out a blanket at the foot of the Wonhyo Bridge and stared at the lights of the 63 Building, a skyscraper that seemed to take the form of two people leaning back to back. There was no one to bother them. As distant traces of music wafted down the shoreline, it was nice simply to enjoy the river breeze and the moon.

The digital world is everywhere and nowhere, a supranational empire that transcends physical borders. Still, there are places that seem closer to its center, places where the pull of the network is particularly strong. Ninety-eight per cent of households in South Korea have access to broadband (versus sixty-eight per cent in America), and seventy-three per cent of the population uses a smartphone (versus fifty-six per cent of Americans). Seoul is a sort of terrestrial embassy for the virtual universe. The city is to high-tech wizardry as Milan is to fashion, or Los Angeles to film. Everything seems a few seasons ahead.

Value Creators & Company (V.C.N.C.), a startup based in Seoul, has created an app for couples like Jimin and Yundi. It’s called Between, “a beautiful space where you can share all your moments only with the one that matters.” It provides a private system by which couples exchange voice and text messages, share photo albums, and post notes on a memo board. A user can send her girlfriend a “sticker”: some, such as a pink bunny blowing kisses, are free; others can be bought from the sticker store for two dollars each. The app’s prize feature is called Memory Box. It’s the color of pine, with a cutout handle—an online depository for photos, notes, and the sorts of keepsakes that once nested in the corners of underwear drawers but now often seem to evaporate, dispersed among e-mail, voice mail, text, and social networks. You can have only one contact on Between—your significant other. If Facebook is a high-school reunion and Twitter is a cocktail party, Between is staying home with a boxed set and ordering pizza.

“No, I like it. I just don’t see the point.”

Since Between launched, in November of 2011, the app has been downloaded 4.5 million times. (Recent competitors include Couple, which offers a “thumbkiss” feature, and an app called Avocado, because “Avocado trees don’t self-pollinate—they need another tree nearby to bear fruit.”) Between has attracted modest followings in countries like Japan and the United States, but in South Korea more than half of twentysomethings have used it. Each month, Between users send one another a collective eight hundred million messages and spend an average of four hundred and fifty minutes using the app. In South Korea, Between has become a synecdoche for commitment: whereas a boy might once have asked the object of his affections, “Do you want to be my girlfriend?,” he now says, “Do you want to Between?”

In April, while the K-pop supergroup Girls’ Generation was conducting a backstage interview for a television show, the phone of one of the group’s members, Hyoyeon, emitted a telltale bloop—the sound that notifies a Between user that she has received a message from her beloved. Gossip sites lit up with the news: “Hyoyeon confirms that she has a boyfriend on TV broadcast!” More recently, a member of Block B, a boy band, released a song called “Ogeul Ogeul” (the title translates roughly as “Cheesy Cheesy”). The lyrics relate a suitor’s apology to his girlfriend, who keeps complaining that he takes too long to reply to her texts. He vows, “We can take photo-booth pictures in Myeong-dong / have a rest, eat dinner / and then add another memory to Between.”

On a sizzling August day, I arrived at Between’s offices, in a modest mid-rise building in Seoul’s Gangnam district. Erin Chang, a sweet and scary-efficient twenty-six-year-old who works in business development, greeted me in the lobby. Chang has a perfect command of Korean and English—she grew up in Seoul and graduated from the University of Pennsylvania—and she translated whenever the situation required it. She also introduced me to some couples who used Between. She led the way to the elevator (a nameplate indicated that the building’s other tenants included an I.B.M. On-Demand Contact Center and something called the Get Rich Project) and then to a large room on the fifth floor, where Between’s twenty-one employees were, unsurprisingly, sitting in front of their computers. Earlier this year, V.C.N.C. raised three million dollars from venture-capital investors, but the headquarters still felt appealingly pre-corporate. A large modular bookshelf hosted a plastic jack-o’-lantern and a desultory collection of coding guides. In the kitchenette, there were fewer kiwis than forty-ounce bottles of beer. The orange and chartreuse bean bags of the reading corner, topped by a cushion in the shape of a dog bone, seemed a decent stab at the self-consciously wacky décor of Silicon Valley. In the middle of the room, six product designers huddled around an iMac, trying to rejigger the way Between’s “album view” function worked, so that a user could search his photos by date. Nearby, a woman was mocking up a flyer, to be posted on Facebook, for a “guerrilla event” that Between was holding that weekend. “Hot summer, Between wants to meet you! :) ,” it read.

Four of Between’s five co-founders—Jake Park, Brad Kim, Lako Cho, KJ Woo, and James Lee—met as students at Seoul National. (They go by English names in their professional lives, because they feel that it helps them avoid the sense of hierarchy encouraged by the many honorifics of the Korean language.) They knew that they wanted to develop an app, and began to think about what was missing from their online lives. Intimacy, they concluded.

“For Between, we started from some deeper things,” Cho told me, as we drank grape sodas in a conference room. “We wanted the offline person to translate into the mobile person.” Three of the founders had girlfriends; to supplement their firsthand experience, they turned to self-help books, which emphasized memory and communication as the keys to fulfillment. They thought: two people. “It’s the smallest unit, but, at the same time, probably the most valuable relationship you’ll have in your life, because it’s the basis of the family,” Chang explained.

The founders conceived of Between as a sort of online sanctuary, an antidote to what Park has called “social-network fatigue.” Between would be the framed photograph you keep on your desk, except that it would also be the desk and all its contents. A sort of sacred space, where love letters don’t mingle with tuition bills, Between seems to encourage reflection. “I want to be a confident, capable man that every Seoul National student looks up to,” Seung Hyun-lee, a user I met, wrote in a memo to his girlfriend. “I will never do anything that makes me look empty or shallow.” He explained, “If it’s a serious message, I want to do it on Between, because if I do it somewhere that I’ve written other messages it lightens it.” One of the highest compliments that the founders have received from a user is that Between feels like a quiet beach.

Cho had come up with a model by which to explain, in the manner of Elisabeth Kübler-Ross, and facilitate the progression of love in the digital age. He called it the Empty Room Theory:

  1. Let’s assume two people who are interested in each other (maybe or maybe not at the beginning of the relationship) are in the same room. This room shouldn’t interfere with their relationship much. It should make them feel like there are only two of them secluded in this place.
  1. The first behavior this couple will exhibit will be “having a conversation.” This is the chatting function of Between. Chatting is the most instant way of communication you can do via mobile.
  1. After that, they may start taking photos to remember the moments they share together. Photo is not as instant as chatting, but it is a great tool for sharing your emotions or memories in the most visual way.
  1. They have shared quite a few memories about happy and sad moments with chatting and photos. Now they might write longer letters to really convey their deep feelings. This is the memo function of Between. Memo is a much slower way of communication compared with photos or chatting, but it conveys the deepest and truest message.

“In my ideal world, I want to memorize everything in my lifetime,” Cho said, longingly. “Photos and locations, but also sounds and smells.”

Young lovers, particularly in South Korea, are a formidable constituency. The taxonomy of blind dates is dizzying: in addition to a bangting, you can go on a sogaeting (kingdom, blind date; phylum, one on one; class, organized by friends or colleagues) or what Koreans call a meeting (blind date, group, a bunch of guys and girls go out to drink and play games). It is not unusual for your boss to set you up (and, if all goes well, you may get taken to a place called the Love Factory Café). Once formed, couples mark every hundred days of their relationship with outings and presents. On November 11th, they exchange Pepero, cookie sticks (side by side, they resemble the number eleven) that often function as meet-cute props, in the manner of the strand of spaghetti in “Lady and the Tramp.” Singles, meanwhile, have Black Day: they eat a plateful of black-bean noodles to console themselves for their lack of Valentine’s Day gifts.

In Seoul, I dropped in at Rainbow Stitch, a boutique dedicated to his-and-hers clothing. It stocked everything from identically polka-dotted tank tops to board shorts and bikinis made from the same Hawaiian-print fabric. (Urban legend tells of a couple in hysterics at the airport: the woman had burst into tears when her boyfriend sat on the wrong side of her and their T-shirts—featuring a slogan that spanned their chests—couldn’t be read properly.) I had gone there at the suggestion of Simon Stawski, a Canadian expat who, with his wife, Martina, runs the popular blog Eat Your Kimchi. “We always describe Korea as having the technology of 2050 with the mentality of 1950,” Stawski told me.

Jake Park, the chief executive of V.C.N.C., has described Between as “a digital couple ring.” Certain ideals—transparency, monogamy—are embedded in its structure. The interface that each partner sees is identical, an insistently placid cocoon of minimalist graphics and muted pinks and blues. The emotional palette—as evidenced by a collection of original emojis—ranges from single roses to bouquets of hydrangeas, Tiffany boxes, and chocolate-dipped strawberries. One of the advantages of using a private app is that you don’t accidentally send a message that was meant for your lover to someone else, but Between is more snuggling than sexting. The design of the software nudges users to constantly express their love. “Some of my friends are married now, and they kind of want to ignore their wives,” KJ Woo told me. “But, on Between, you can see if someone’s gotten a message you sent them, because the red heart next to it disappears once it’s been read.”

To some people, Between provides welcome ballast to the free-floating sensation of interacting online. For others, it sounds like a digital handcuff. (Between’s founders considered adding a location-tracking feature, but they decided it was too stalkerish.) A one-e-mail-address, one-account policy makes it difficult to maintain multiple relationships. Woo continued, “A user complained to customer service, ‘I have to use two user names and log in and out to date different men.’ ” The app offers its users the style of online romance while providing the protection of an old-fashioned courtship. Four million people are walking around wearing couples’ outfits that only they can see.

It was July. Not long after Yundi fell in love with Jimin, she left for an extended trip with her family. Her parents hadn’t met Jimin, but they saw all the pictures that the couple posted on Kakao and Facebook.

For two weeks, as she travelled through Europe, Yundi sent pictures on Between, just for Jimin: there she was, throwing a coin over her shoulder into the Trevi Fountain; in Holland, in front of a windmill, making windmill ears with her fingers; outside a Tyrolean castle, her plastic poncho inflating in the wind as though she were a doughboy. In Florence, she posed outside the Duomo, lifting her hands to her cheeks to form a little megaphone. As church bells rang, she used a paintbrush app to superimpose words on the image so that they seemed to be coming out of her mouth. She drew a heart around them and pressed send: “Ti amo, Jims.”

The time difference meant that, whenever they woke up, there was a memo waiting, like a letter slipped under the door. Yundi wrote, from Venice:

I woke up at 5:30, and, at 7:30, started sleeping on the bus. I was so bored that I started watching a lot of movies. Our driver was Italian, so he talked a lot. People bought a lot of olives in Venice. Makoli is so expensive here, and the data roaming sucks, so I couldn’t really talk to you on Between.

Jimin replied:

Oh, they sell makoli there? Funny.

They exchanged reams of memos. Yundi normally thought that the term “soul mate” was trivial, but she and Jimin felt that they might spend their lives together. They started a list that they called the “soul-mate memo.” They were both only children. Their mothers had had them very young, their little fingers were short, and they hated cucumbers. They both owned a Galaxy, they both used Android, they both got a lot of mosquito bites, they both liked attention, they both had to hold a pillow to go to sleep. They had seventy-two things in common. They decided to find more when Yundi got back to Seoul.

It is easy to forget that when the Korean War ended, in 1953, South Korea was one of the world’s poorest countries, with a per-capita income of less than eighty dollars a year. In 1961, Park Chung-hee seized power in a coup. Presiding over a military dictatorship, he carried out an ambitious program of industrialization that helped transform South Korea into the world’s fifteenth-largest economy—“the miracle on the Han River.” When the Internet came along, the country was well positioned to exploit its possibilities. James Larson, the author of several books on telecommunications in South Korea, writes, “While Vice-President Gore spoke about the ‘information superhighways,’ Korea set about to actually build them.”

Mobile phones came early to South Korea, eclipsing landlines by 1999. (This didn’t happen in the U.S. and China until 2003.) But data services were expensive, and a series of protectionist measures enacted by the government meant that South Koreans’ choice of smartphones was limited largely to those manufactured by Korean companies. In 2008, fewer than one per cent of South Koreans used smartphones. Honduras and Guinea-Bissau had the iPhone before South Korea. In November of 2009, when the government finally allowed Apple to enter the market, commentators spoke of “iPhone shock.” Soon, the domestic manufacturers had improved their products and made their prices competitive.

One day, I visited Jong-Sung Hwang, the head of the national I.T. Policy Group at Korea’s National Information Society*. “We experienced huge changes in the nineteen-seventies,” he said, when I asked about the origins of South Korean technophilia. “People who moved fast benefitted big.” Looking forward, Hwang detailed Smart Seoul 2015, a seven-hundred-and-ninety-two-million-dollar plan to make Seoul the world’s most sophisticated municipality, if it isn’t already. Among other initiatives, the plan calls for free Wi-Fi at ten thousand intersections, public parks, markets, and bus stops (“You shouldn’t be able to walk more than five minutes in any direction without access”) and mandatory recycling logged by an R.F.I.D. tag issued to each household (“South Koreans like learning something new”). Schools are phasing out paper textbooks in favor of tablets. “We think digital technology is not a luxury but a basic right for city living,” Hwang said.

South Korea—despite its infrastructure, its openness to adaptation, and its education system, which consistently ranks among the top in the world—has yet to produce behemoths like Google and Twitter (neither of which is especially popular with South Koreans, who prefer to search with Naver, a Korean-language search engine, and to social-network with Kakao, a mobile platform that offers everything from messaging to games). South Korean technology companies have a reputation as “fast followers,” leading in manufacturing but lagging in innovation. Digital life, while thriving, is more heavily regulated than in most democracies: you need a state-issued identification number to use the Internet at Starbucks, and political discussion, particularly in support of North Korea, is often censored. In 2010, South Korea blocked @uriminzok (“our people”), a Twitter feed run by the North Korean government. “The expansive controls on online speech established in South Korea . . . prevent citizens from accessing valuable expressive, historical, political, and artistic online content,” the Electronic Frontier Foundation wrote in 2011, in an open letter to Korea’s Communications Standards Commission.

This year, in the hope of establishing a South Korean Silicon Valley, the newly elected President, Park Geun-hye (she is Park Chung-hee’s daughter), pledged almost a hundred million dollars in subsidies and grants to startups. “The creative economy puts priority on human creativity,” President Park said, in April, as she welcomed Bill Gates to the Blue House, Korea’s Presidential residence. “The government needs to extend opportunities for talented people so that they can establish businesses by taking risks.”

It was August. Yundi had cut her hair after she got back from Europe. It was wavy now, and tinted auburn. She had a green half-moon on every other fingernail. She was so into using Between that she had applied for an internship with the company, and was accepted. One afternoon, she wore a floral circle skirt, a white Guess T-shirt, and coral-colored lipstick. She carried a colorblock tote. Jimin had on shorts and a navy-blue Guess shirt. They both wore beige baseball caps embroidered with pixellated monkeys. His rooted for the Dodgers, hers for the Yankees. Yundi loved it when he wore his hat backward—she thought it made him look like a rascal. They had been together for seventy-nine days.

At a coffee shop, Jimin presented Yundi with an exquisitely wrapped box. Inside, a Super Soaker water gun lay on a bed of iridescent tinsel. Yundi squealed and did a little dance that always appealed to Jimin. They had recently seen a movie in which Bruce Willis gives his girlfriend a gun, and they were going to the Caribbean Bay water park the next week.

The trip was part of a bucket list that they had decided to compile. They shared it on Between and edited it daily. To do: go to Jeju Island, do a piggyback ride, go on a trip in a camping car, throw a party, stage a solo piano recital, go back to Room 206 at Phoenix Park. Jimin wanted to go on a theme date where they’d wear hats and dark glasses and set the timers on their cameras so it looked like they were being chased by paparazzi.

The summer was a daze. At the water park, they floated on inner tubes down a lazy river, laughing as they soaked unsuspecting tourists with the water gun. They went to baseball games and ate in restaurants. They sent each other a hundred messages or more a day; on weekends, when they were together, they sent fewer. When they video-chatted, they took screen shots. Yundi found the screen shots to be very natural, in a way that was different from the posed pictures they took while they were out on dates. Looking at them made her realize how happy she was when she talked to Jimin.

Jimin, who had a new job, had to spend his birthday in Yongin, at a company workshop. Yundi showered him with gifts. She made origami—lips, a heart. She used Photoshop to draw a series of black-and-white portraits of the two of them that formed an animation—she highlighted their hair in neon colors, in a way that brought to mind Clementine, in “Eternal Sunshine of the Spotless Mind.” She called the sequence “How to Kiss.” Yundi sent a video of herself singing a song to Jimin. She also sent him a grid of photographs in which she held up handwritten speech bubbles. “I love you,” they read. “Thank you for being born.” Jimin bragged about it all day to his co-workers. He and Yundi didn’t believe in mil-dang (“push-pull”), the Korean version of hard to get—why push away the person you loved?

One day, Yundi smelled smoke on Jimin’s breath after he came out of the bathroom. She hadn’t asked him to stop smoking—he had declared that he wanted to quit, to be a better boyfriend. Yundi didn’t really care about the cigarettes. She took the fact that Jimin had started smoking again as a sign that he loved her less. She got mad and, despite his apologies, left.

When she got home, she checked her phone. There was a memo from Jimin:

I made a really big mistake today. I don’t even have enough time to make my girl laugh, but I made her cry. (Sorry.) From August 23, 2013, I will really, really quit smoking, and I will never make her cry. Love, Jimin.

The combination of technological prowess and couples culture makes South Korea a particularly advanced laboratory for the study of digital love. One Saturday morning, I joined a handful of Between employees for the “guerrilla event” that they’d been planning. Their aims were anthropological as well as promotional: they wanted to glean information from users about why, how, and when Between fit into their romantic lives. (Between’s expertise has appealed to American startups looking to enter the Asian market—when Uber, the taxi-hailing app, launched in South Korea recently, it offered Between users a discount.) The heat wave persisted. We all donned turquoise Between T-shirts that soon turned a deeper shade of green. We began at Deoksugung, a complex of ancient palaces near City Hall—a notorious date spot. (What a date spot needs, more than anything, is to be known as a date spot.) Couples, noticing the T-shirts, flocked toward the group. The ones who had R.S.V.P.’d via Facebook received personalized thank-you notes, which an employee’s girlfriend had calligraphed and illustrated. “Hi! How are you? This is Between,” one of them read. “Between is rooting for your beautiful romance!”

“Back hug!” an employee yelled, calling out his favorite pose as he snapped a couple’s photograph. (Later, Between published a gallery on its Facebook page.)

We moved on to Cheonggyecheon, a park bisected by a sunken stream. People sat on the banks, cooling their feet. A guitarist was performing “My Way.” A swarm of couples materialized: couples drinking iced coffee, couples wearing backpacks, couples carrying stuffed animals, couples dressed all in red.

A girl in a striped shirt—her boyfriend was wearing one, too—approached and said, “I use Between every day, and there was an error yesterday.”

I wasn’t really paying attention. I was sending pictures of a butterfly to my husband, using Between’s chatting function.

Bits of conversation floated over—the intense, sometimes unsettling fragments of love in the digital age. Among the things I heard, that afternoon and that week:

“It was an explosion of my emotion.”

“I actually deleted the app once, when we had a huge fight.”

“He thinks it’s humiliating for a guy to hold a girl’s handbag, but he does it when I ask him.”

“That one was too weird to upload to Facebook.”

“He has a very old-fashioned hobby, which is collecting CDs.”

“In the beginning, I would make sure all the photos were perfect.”

“Now I kind of regret having deleted it.”

One girl’s phone passcode was 5148, and her boyfriend’s was 5368: on a keypad, each formed half of a heart.

The users shared their memos:

“I wish all of my shoes had shoelaces, so that you could tie them for me.”

“I took this photo because my mom wanted to see your face.”

Another couple had imported a thirty-page document to their Memory Box. It was called OurFuture.

About a year after Between launched, a letter arrived in the mail at headquarters. (The actual mail.) “Thanks to your app, we were able to exchange many words of love with each other,” a user had written. “And now we are getting married.” The user went on to invite the entire staff of Between to the wedding.

Sherry Turkle, the director of the M.I.T. Initiative on Technology and Self, has spent three decades considering the ways in which technology affects relationships, thought, and attachment. In “Alone Together” (2011), she writes, “We bend to the inanimate with new solicitude. We fear the risks and disappointments of relationships with our fellow humans. We expect more from technology and less from each other.”

“Pop-up prison.”

Turkle writes persuasively about the ways that the “continual partial attention” that our devices induce (and demand) denature human connections, even tenuous ones. “At a café a block from my home, almost everyone is on a computer or smartphone as they drink their coffee,” she writes. “These people are not my friends, yet somehow I miss their presence.” In her view, romantic relationships, the most intimate of intimacies, are particularly susceptible to being diminished by the “emotional shorthand” that the digital world demands. “A lot of people are going through the torments of the damned,” Turkle said recently, over the telephone. She spoke of college students who can’t send a text without a ghostwriter; online daters paralyzed by the tyranny of choice; a woman who was unable to stop herself from opening Tinder, the hookup app, when her boyfriend got out of bed in the middle of the night.

“I think we’re on a learning curve,” Turkle told me. “ ‘Alone Together’ represents us at the darkest moment. I wrote that book when people were saying, ‘Don’t be silly, this is our greatest achievement.’ Eric Schmidt, then the C.E.O. of Google, was telling people that, in the future, you’ll never have to be lonely or bored again.”

Anyone who has experienced the jittery expectancy that texting can incite—accompanied by phantom vibrations and the ability to sense that your screen has lit up, even under a pile of ten coats—knows that communications can thwart communication. When the text arrives, the Pavlovian anxiety of waiting momentarily subsides, but the angst over what to make of the content escalates. “Analyze!” the call goes out, as messages are forwarded and phones are passed around tables, as though Rosa Mexicano were Bletchley Park. Falling in love turns into an exercise in code-breaking.

At the Samsung exhibition store in Seoul, I encountered an app called Textat, a “sentiment analysis service”—a sort of automated HeTexted.com—that uses algorithms to parse a correspondent’s text messages, in order to establish his “current emotional state.” The readout includes a list of the top five sentences that the correspondent has used to show affection, and a graph of how many texts he has sent daily, weekly, and monthly. (There is something creepy about the way technology acts as a third wheel in relationships, but who knows? A few years ago, it would have seemed pathological to send an e-mail to someone who was in the same house, or even the same bed; now not so much.)

When things go wrong in a relationship, the persistence of the online world’s memory is often painful. Facebook suggests that you friend your former girlfriend; Gmail auto-fills her e-mail address each time you type the first letter of her name. There’s a paradox implicit in products like Between—technologies intended to help people regain what they’re losing because of technology. At least to people who came of age in an era when the wholesale destruction of the artifacts of a relationship required fire, it is jarring to find—wedged among updates on voice-mail upgrades and Halloween stickers—a notice entitled “How to: Disconnect & reconnect your relationship.” Originally, you could delete a Between account with the touch of a button. But, faced with an average of three hundred restoration requests a day from “dramatic deleters,” Between has instituted a policy that tries to chart a middle course between instant gratification and lasting regret: the data of a user who chooses to “Disconnect Partner” remain hidden but available (“Restore Memories”) for thirty days.

Turkle writes, “When interchanges are reformatted for the small screen and reduced to the emotional shorthand of emoticons, there are necessary simplifications.” But aren’t there complications as well—ways in which the digital world enriches and amplifies our romantic experiences? Many of the couples I met in Seoul seemed to use Between as a sort of personal trainer for their love lives, reminding them of their commitment, and cheering them on when they reached their goals. The concept of physical separation obtains even in notional space, and the online world, with its infinite area, can offer a sense of clarity and expansiveness. If the online world has come to feel like sprawl, a medium like Between proposes a sort of new urbanism—the information superhighway with corner stores and bike lanes. “Offline relationship > online relationship,” Erin Chang wrote to me in an e-mail. She appended what she said was one of the Between team’s favorite quotes, from the British pop philosopher Alain de Botton: “True love is a lack of desire to check one’s smartphone in another’s presence.”

Several years ago, if you had asked me whether smartphones were just modern delivery systems for a static set of feelings, I would have said yes, but after my husband and I spent two years commuting between two countries I came to think that they enlarged our repertoire: we could send a text that said, “I miss you,” we could share videos of a duck that kept landing on the roof, we could take a picture of a good meal or a funny headline (a shot without commentary of a newspaper that says “Panther on the Loose” was more amusing than an e-mail saying, “I saw a newspaper today that said there was a panther on the loose”). Simon Stawski, of Eat Your Kimchi, suggested that the way a couple communicates online amounts to “a new language of love.” If so, emojis constitute a surprisingly eloquent register. They seem not only to express feelings but also to create new ones—hundreds of micro-sentiments expressing delicate gradations of emotional weather. There’s the yellow character that somehow combines the serenity of the man in the moon with the manic cheer of a smiley face, blowing a kiss. The flamenco dancer who seems to shimmy. The blameless hatching chick. The oddly endearing pile of shit. Writing “Why didn’t you clean the bathroom?” is obnoxious; 🚿 🛀 😈 gets the point across but is also flirtatious. There is no word for “bashful face with pinkening cheeks that obliquely suggest I’m both embarrassed and pleased.” You just have to send a text.

It was November. Yundi was back in school, struggling with her assignments. Overseeing part of a project designing solid-state drives, Jimin was working long hours and, often, on weekends.

Jimin didn’t know it, but Yundi was going through a hard time. It wasn’t really about him. She felt stalled, a little bored with her life. She stayed up late watching movies, unsure how to channel her artistic impulses.

Occasionally, when Yundi felt this sense of ennui take hold, she went on Between and immersed herself in the splendor of the digital world that she and Jimin had created. It was all there: the night they rode by the Han River on a motorcycle with pink balloons, the soul-mate memo, the water-gun fight, the birthday animation, the bucket list. Even the reminder of the time that Jimin had smoked in the bathroom remained. They did not want to delete their traces. Yundi sat on the train, head bent, her phone in her hands as though it were an illuminated manuscript. ♦

*An earlier version of this article referred to Korea’s National Information Security Agency; it is the National Information Society Agency.