Cha Dohyeon is in line to be the successor of Seungjin Group. No one in his family is aware that he's been suffering from dissociative identity disorder for years following a family tragedy. Oh Rijin is a first-year psychiatric student who runs into one of Dohyeon's many personalities while looking for one of her patients.

Falling in love at first sight with Rijin, Shin Segi vows to get rid of his host Dohyeon. Dohyeon looks for ways to make sure to keep his various personalities in check while he assimilates to life in Korea again.

Dohyeon feels guilty when he finds out that he inadvertently put Rijin in danger because one of his alter egos. Rijin figures out the truth of his condition and sympathizes with him.

Considering his instability a risk to himself and others, Dohyeon declines treatment and withdraws from people and work. Seungjin Group harbors a deep family secret kept hidden from Dohyeon, who also discovers a new personality has emerged.