Psychopath Diary

Yook Dong-sik (Yoon Shi-yoon), an analyst who works at Daehan Securities, has a timid personality. He can't even get angry at the people who look down upon him. One day, shortly after failing on his attempt of suicide, he witnesses a murder. He unintentionally picks up a diary belonging to the murderer, on which was written the log of his murders. He flees with the diary, but he is accidentally hit by Police Officer Shim Bo-kyung's (Jung In-sun) patrol car which causes him to suffer from retrograde amnesia. Due to the diary in his possession, Dong-sik mistakenly believes he is a psychopath. Since that moment, his behavior started to change. Bo-kyung, who got involved with Dong-sik, decides to catch the serial killer. Meanwhile, Seo In-woo (Park Sung-hoon), the director and son of the chairman of Daehan Securities where Dong-sik works, turns out to be the heartless psychopath serial killer. He loses his diary when his 6th victim, a homeless old man tossed his diary away. He feels insecure ever since, He is obsessed and in love with DongSik .