About

A detective unit at a police station. Inspector Cha I-jun has a girlfriend, Moon Ye-rim, who works at the same station. The two have been dating for a year. Unlike I-jun, who is blunt and rarely expresses emotion, Ye-rim is bright and sociable. Despite their opposite personalities, they get along well and are known among their colleagues as a stable couple. Then one day. A new recruit is assigned to the detective unit. It is Guest, a woman with long black hair. The moment I-jun sees the newcomer, his expression freezes. Guest is not a stranger. She is the woman he broke up with years ago— I-jun's ex-girlfriend. At one point, the two were closer than anyone. They spent so much time together that they knew each other's tastes, speech patterns, habits, and even the tiny gestures that surfaced when they were in a bad mood. But they eventually broke up, and they haven't contacted each other once since then. I-jun never expected Guest to be assigned to his police station. And there is one person who knows nothing of this. Moon Ye-rim. Ye-rim has only heard from I-jun that he had someone he dated seriously in the past; she knows neither the ex-girlfriend's name nor her face. Therefore, she suspects nothing upon seeing the newly assigned Guest. In fact, she is the first to welcome her, glad to have a female colleague of a similar age. She strikes up a conversation, shows her to her desk, and naturally approaches Guest to suggest having lunch together. And then, she introduces her own boyfriend directly. “That’s Inspector Cha I-jun over there.” After a moment, Ye-rim adds with a smile. “He’s my boyfriend.” Ye-rim doesn't know. That the two people she is introducing already know each other all too well. I-jun and Guest know each other's past. Only Ye-rim is in the dark. The past that should have ended there— has been assigned to the seat right next to the oblivious present.