Kwon Jungwoo is a rising basketball star on the university campus, while former star Han Jiwon starts his university life trying to stay out of the spotlight. One day, Jiwon spots Jungwoo practicing alone in the empty gymnasium and is unintentionally drawn to him. Later, through a series of misunderstandings, a casual remark changes their relationship forever.

Han Jiwon deliberately avoids Kwon Jungwoo, but they keep running into each other and even become group members. After Jungwoo announces his breakup with his girlfriend, the two began to interact more frequently and meaningfully; Jiwon realizes he has fallen in love.

Han Jiwon and Kwon Jungwoo prepare a class report together, and the relationship between the two grows warmer. However, Jiwon receives a confession from a schoolmate, which makes Jungwoo feel jealous and concerned. After a dinner party, Jungwoo takes a walk with Jiwon, and Jiwon gathers the strength to invite Jungwoo home with him.

Jungwoo fantasizes about Jiwon despite being ill while rejecting Jiwon’s concern. When he sees a photo of Jiwon with his younger brother, he is overcome with jealousy and finally realizes his feelings. When Jiwon visits him in the dormitory, he makes his move.

Jungwoo's confession makes Jiwon feel that he’s been put in a bind, and is scared how their relationship might l affect their future. He asks for two weeks to think about it, and Jungwoo smiles and says he'll try his best to woo him. Jungwoo comes out in front of his friends, which shakes up Jiwon even more, which eventually leads him to talking about his feelings.

Jiwon's relationship with Jungwoo begins. While sharing a bed, Jiwon has trouble coming to terms with Jungwoo's intimate behavior and his classmates' teasing, leading him to hide his relationship. In the middle of the night, Jiwon confesses his insecurities and fears, while Jungwoo's gentle embrace makes them more courageous to fall in love.

Online gossip alleges that Han Jiwon and Kwon Jungwoo are secretly dating. Won chooses to remain silent and distant in order to protect Jungwoo's career. Meanwhile, Jungwoo is injured during training, and the pressure from his coach and lack of contact with Jiwon causes him to have an emotional breakdown, putting their relationship to the test.

After an argument, Jiwon and Jungwoo kiss and make up. The next day, Jiwon takes the initiative to disclose his love, and Jungwoo uses the number “18” on the back of his jersey to symbolize the most precious person in his heart in a media interview. They no longer run away from each other and instead choose to love each other openly.