Because of his troubled past and obsessive—compulsive disorder , Jae-yeol can only sleep in his own bathtub. From his first meeting with psychiatrist Ji Hae-soo on a talk show, they have had a combative relationship.
When noise from ongoing construction beside his house interrupts his writing, and he learns that Hae-soo is currently a tenant living in a building he owns in Hongdae , Jae-yeol temporarily moves in with her and her housemates because of his fascination with her. As the two fall in love, they must later come to grips with Jae-yeol's undiagnosed schizophrenia.
A smart and compassionate doctor but not very affectionate. His wife and children are based in the United States, and he has an amicable relationship with his ex-wife and colleague, Young-jin. After he becomes the court-appointed psychiatrist to a convict, Jang Jae-beom, whom he later finds out is Jae-yeol's brother, Dong-min sets out to find the truth behind the crime.
He is particularly close friends with Dong-min, who often calms him down during his panic attacks. Soo-kwang is unlucky in love and keeps getting dumped by girls, but the one he can't quite get over is So-nyeo, who is not only a minor but has several boyfriends at the same time.
Do Kyung-soo as Han Kang-woo A high school student who's a big fan of Jae-yeol, and aspires to become a famous author like him.
Kang-woo constantly bugs Jae-yeol to read his manuscripts, and follows him around. He and his mother are frequently beaten by his alcoholic father. Kang-woo is later revealed to be more than just a fan to Jae-yeol. Jae-yeol first saw Kang-woo three years ago, ever since Jae-beom stabbed him.
Young-jin still has unresolved feelings towards her ex-husband Dong-min, since the breakdown of their marriage was partially caused by her decision to focus on her career and not have children. Lee Sung-kyung as Oh So-nyeo A troubled girl who got expelled from high school and was abandoned by her mother. So-nyeo works at a cafe alongside Soo-kwang; she takes advantage of his feelings for her and uses him to give her money and buy her things, even though he knows she's seeing someone else.
So-nyeo eventually falls for Soo-kwang and begins dating him exclusively, then decides she wants to become a psychiatrist like Hae-soo. Yang Ik-june as Jang Jae-beom Noh Tae-yub as young Jang Jae-beom Jae-yeol's older brother who served eleven years in prison after being found guilty of killing their abusive stepfather.
His defense attorney at the time found the verdict and sentence needlessly harsh, which came about due to a tough-on- juveniles judge and an ambitious prosecutor. Jae-beom has maintained his innocence through the years, but after being released, he repeatedly stabs his brother, and gets sentenced to another 30 months in jail. Violent and unstable, Jae-beom can't wait to get out of prison and get his revenge on Jae-yeol, whom he believes is the real murderer.
Cha Hwa-yeon as Ok-ja Jae-yeol and Jae-beom's mother. She and Jae-yeol have a close, affectionate relationship. Her older son Jae-beom believes that Ok-ja gave false testimony against him at his trial in order to save Jae-yeol.
But as Dong-min later learns from Jae-beom's defense attorney, Ok-ja was the true culprit, setting fire to her unconscious husband after one of her sons non-fatally stabbed him the man's cause of death was asphyxia. The psychologist who examined her at the time diagnosed Ok-ja as suffering from dissociative disorder , a defense mechanism which made her forget what happened and what she'd done. Tae Hang-ho as Tae-yong Jae-yeol's best friend from childhood and an employee at his publishing house.
Tae-yong betrays Jae-yeol by giving Pul-ip a galley proof of his latest book, but Jae-yeol forgives him. Kim Mi-kyung as Hae-soo's mother She takes good care of her severely handicapped husband, but is also having a decades-long affair with another man, Mr. Hae-soo's aversion to physical intimacy stems from her knowledge of her mother's affair.
They break up when she learns that he's been unfaithful to her. Choi Seung-kyung as Oh Do-deuk, Yoon-soo's husband. Han Jung-hyun as Editor Bae, Jae-yeol's book editor. Myung Jong-hwan as Resident, Hae-soo's colleague. Lee Seo-joon as Resident, Hae-soo's colleague. Special appearances[ edit ] Yoon Jin-yi as Lee Pool-ip ep A magazine journalist who goes after an interview with Jae-yeol because she's a fan of his work, and ends up becoming his girlfriend for three years. Pul-ip later steals his latest book and passes it off as her own, then publicly accuses Jae-yeol of plagiarism.