Shin Yu-jin, a clumsy male friend with shaggy hair who only knew about studying. He, who was foolish, changes 180 degrees and shakes Kang-hee's heart. “I can’t watch you with other guys pretending to be friends anymore.” Her fluttering first love that started like that, Yoo-jin leaves in an unexpected accident, leaving Kang-hee with a trauma. Eight years later, Kang-hee became a homicide detective. She's been on an undercover job for a week and she meets a strange man in a hotel lounge. A face and coupling that resemble Eugene's. Confused by her confusion, Kanghee ruins his seat, and the two continue to get entangled due to an inevitability like a coincidence...