Season 1 - High School Return of a Gangster

Kim Deuk Pal is a 47-year-old gangster who is the #2 guy in his gang. He doesn't have an educational background due to his poor parents, but he dreams of attending a university. Deuk Pal has been studying to achieve his dream, but it's not easy. One day, he sees a young man, Song Yi Heon, about to kill himself. At that time, Deuk Pal's spirit possesses the body of the suicidal 19-year-old high school student. Deuk Pal soon learns that Yi Heon is a victim of bullying, which has caused him to want to take his own life.

Now, in Yi Heon's body, Deuk Pal takes on the bullies to punish them and becomes friends with classmate Choi Se Kyung. Se Kyung is a model student who appears to be in a perfect situation but suffers from domestic violence at home by his father.