The following version of this book was used to create this study guide: Park, Sang Young. Love in the Big City. New York: Grove Press, 2021.

In Part I, Young is 20 years old and he meets a fellow student at his college named Jaehee. They meet outside of a bar where Young is kissing another man. He asks Jaehee not to tell anyone at their college he is gay and she agrees. Later, he defends her when some upperclassmen are calling her promiscuous. Young and Jaehee move in together. Much of their friendship revolves around their mutual interests in drinking and meeting men for sex. One day, Jaehee comes to Young and tells him she is pregnant. He tells her he will pay for her abortion and accompanies her to a women's health clinic. While there, he recalls visiting a different health clinic with his boyfriend, an engineering student, a short time earlier. He overheard a male nurse use a gay slur to describe him and his boyfriend. At the women's clinic, the doctor refuses to perform an abortion and lectures Jaehee about her sex life. Furious, she steals a 3D model of a uterus. She later returns it to a nurse, who tells her where she can get the abortion. Shortly after this occurs, the engineering student comes to their apartment late at night, angry because Young broke up with him. Jaehee calms him down and sends him on his way.

Her senior year, Jaehee gets a job at an electronics company, where she meets a man she quickly develops a serious relationship with. When her boyfriend discovers she is living with Young, Jaehee tells him he is gay so he will not be jealous. Young feels like this disclosure is a betrayal and stops speaking to Jaehee for three months. He learns that the engineering student died in a car accident. When he gets back in touch with Jaehee, she is engaged. She asks Young to be the emcee at her wedding, but later tells him that her fiancé’s best friend is going to be the emcee instead. She moves out of the apartment she shared with Young.

In Part II, Young is in his early 30s. He finds his diary from five years earlier in his mailbox. He had given this diary to his boyfriend, who he calls hyung, when they broke up. Hyung has left editorial marks in the diary and a note telling Young he wants to see him. Young goes to meet his terminally ill mother at the hospital.

Five years earlier, Young and hyung meet in a philosophy class. They begin having dinner each week after class, and this develops into a romantic relationship, despite the fact that hyung is ashamed of his sexuality and determined not to reveal it to anyone. He is also judgmental toward Young, frequently lecturing him about politics. Despite these red flags, Young stays in this relationship because he loves hyung. All the while, Young is looking after his ill mother. He recalls how his mother left his father when she discovered he was unfaithful. She then raised Young on her own while running a successful matchmaking business. When Young was a teenager, she sent him to a psychiatric hospital after witnessing him kissing another boy, and Young is still angry about this. Hyung ultimately breaks up with Young, telling him that he was never in love with him. Young imagines that the sense of loss he feels must be similar to how his mother felt when she learned Young's father was having an affair, and how she felt watching Young grow up and away from her. He tears his diary up into pieces and flushes them down the toilet.

Part III takes place several years later. Young is at a bar with friends, one of whom picks a fight with the DJ. When pulling back his fist to throw a punch, Young's friend accidentally hits Young in the face. The bartender holds a bottle of water to Young's face, and Young kisses him. He then realizes this was a mistake. His lip was bleeding and he could have infected the bartender with HIV, which Young contracted from a boyfriend years earlier.

The next day, the bartender, named Gyu-ho, finds Young at work and returns his phone case, which was lost in the shuffle the night before. There is a mutual attraction and they begin dating. Unlike Young's previous boyfriends, Gyu-ho is a kind and caring person. He comes all the way across town just to hang Young's curtains. They rarely have sex, because Young does not wish to transmit HIV to Gyu-ho. They visit Thailand together. The relationship ends when Gyu-ho takes a job in China and Young cannot go with him because his HIV+ status would be detected on a blood test. As he is leaving, Gyu-ho asks Young if they are breaking up and if Young cares that they will not be together anymore. Young does not respond, but he returns home heartbroken.

In Part IV, two years have passed since Gyu-ho and Young's breakup. Young returns to Thailand with a businessman named Habibi he met on a dating app. It seems to be a relationship based on sex and companionship, not love. While in Thailand, Young remembers all of the places he visited with Gyu-ho, and he is consumed by longing. He recalls a trip to Wolmido Island, in which they saw a woman passing out lanterns. She said they could write their wish on a lantern and release it into the sky. Young wrote and then crossed out multiple wishes before writing Gyu-ho's name. However, all of the crossing out had torn the lantern, causing it to fall from the sky.