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 has a dream of attending a university. He 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 possessed 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, Deuk Pal, in the body of Yi Heon, 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 he suffers from domestic violence at home by his father.
วิญญาณของนักเลงที่ออกจากโรงเรียนตอนมัธยมปลายและบังเอิญมาติดอยู่ในร่างของเด็กหนุ่มวัย 18 ปีที่ฆ่าตัวตายกลับไปยังโรงเรียนมัธยมปลายอีกครั้งเพื่อแก้แค้นเหล่าแก๊งเด็กชอบบุลลี่ด้วยทักษะนักเลงของตัวเองและพบเจอกับความสัมพันธ์ที่คาดไม่ถึง