Lee Jae-hoon, who lives in a Seoul goshiwon (exam study room), lives a numb life filled with deprivation and inferiority. On a hot summer day, he begins to post stories about his love life in an anonymous chat room. Amidst the unexpected attention and acclaim, he feels alive for the first time. Triggered by his flirtation with the woman in Room 3 and his relationship with 'Coco Rose' from the open chat room, he begins to make increasingly dangerous choices.