Jang Jaeyeol is a writer of bestselling mystery novels and a radio DJ. Playful and a bit arrogant, he also suffers from obsessive–compulsive disorder. Ji Haesoo is a psychiatrist on her first year of fellowship. Driven and ambitious with her career yet compassionate towards her patients, Haesoo has a negative attitude towards love and relationships in her personal life. Once Jaeyeol and Haesoo meet, there is much contention between them caused by their strong personalities and refusal to give in to each other. But slowly their bickering turns into love, and they begin to learn how compatible they are. Jaeyeol and Haesoo attempt to heal each other's deep-seated wounds, but their fledgling relationship takes a blow when they learn that Jaeyeol's mental health issues are more serious than they initially suspected.

• Zo In-sung
• Gong Hyo-jin
• Sung Dong-il
• Lee Kwang-soo
• Jin Kyung
• Lee Sung-kyoung
• Doh Kyung-soo
• Yang Ik-june