"Psychopath Diary" is the story of Yook Dong Sik who coincidentally picks up the diary of a serial killer.

Nan Hee is an ugly girl and this has influenced her to become mean. One day, she receives a ring which holds a family secret. Se Gun is handsome, but he has a cold-blooded personality. Due to the magic of the ring, he declares Nan Hee as his ideal woman with a beautiful appearance.

When Jo Yang Sun is driven out of house and home after her father is framed for a crime, she is forced to crossdress in order to make ends meet as a bookseller, where she meets Kim Sung Yeol, a handsome, but mysterious scholar who is actually a vampire. Meanwhile, an evil presence at the royal palace stops at nothing to keep the Crown Prince from claiming his rightful throne.

Despite being married and having a fulfilling career as a sophisticated arts foundation director, something is missing in Oh Hye Won's life. When she meets twenty-something Lee Seon Jae, Hye Won's appetite for passion is awakened, and she soon falls for the impoverished piano prodigy. Though they risk everything, Hye Won and Seon Jae can't help but embark on an affair that threatens to destroy both their lives. Based on the 2005 Japanese film Tokyo Tower, this romance aches with the desperate struggle between love and reality.