After suffering from various obsessive-compulsive disorders and having the worst day of her life, Won Do-Yeon's house is infested with cockroaches. Unable to bear the urge due to her obsessive-compulsive disorder, Do-Yeon asks deliveryman Bok Geum-Ho to exterminate them. However, Geum-Ho, rebuffed by his out-of-the-blue advances, throws the roaches into Do-Yeon's home instead. Do-Yeon eventually hires a cockroach exterminator from a secondhand goods trading platform. Geum-Ho, who has fallen in love with Do-Yeon, becomes jealous of her. Panicked by the roaches, Do-Yeon seeks help from her father, Won Hyuk-Su, who lives in the countryside. He heads to Seoul to reunite with his daughter, with whom he has lost contact. Won Hyuk-Su, the exterminator, and Bok Geum-Ho gather to exterminate the roaches, but someone dies on the spot. This incident triggers a series of cockroach-related incidents, rewriting Won Do-Yeon's family history, torn apart by her obsessive-compulsive disorder.

(Source: Kakaopage, translated)