A talented martial artist who can't walk past a person in need unites with a probation officer to fight and prevent crime as a martial arts officer.

Seung-jin, who is preparing for an audition to pursue his ambition of becoming a singer, moves into a new studio apartment. On the first night, as he just started to settle in, he hears a woman wailing from next door. With all the noise she makes owing to her badly soundproofed room, La-ni has driven away several neighbors. Seung-jin isn't one to back down easily. Their argument intensifies to the point that they have discovered everything about one other's life through their noises save for their names and faces.