Park Sung-hoon is a South Korean actor. He is best known for the roles in the television dramas Psychopath Diary (2019), Justice (2019), My Only One (2018 - 2019), Rich Man (2018), Mad Dog (2017), Black Knight: The Man Who Guards Me (2017 - 2018), Don't Dare to Dream (2016), Six Flying Dragons (2015 - 2016), Three Days (2014), You Are the Boss! (2013) and Bachelor's Vegetable Store (2011 - 2012).
Yook Dong-sik works in a brokerage company. One day, he witnesses a gruesome murder and comes across a diary that contains a detailed list of the murder logs. He flees and gets into a car accident. He lost his memory and thought that he is the psycho serial killer. His personality changes drastically.