My Strange Hero (2018)

When Kang Bok Soo was a secondary school pupil, he was falsely accused of committing an act of violence and was expelled from school. This was caused by his first love, Son Soo Jung, and another pupil, Oh Se Ho. Kang Bok Soo is now an adult, but his life has not gone smoothly. To take revenge on Son Soo Jung and Oh Se Ho, he returns to the same secondary school disguised as a pupil. The school environment has changed, and Kang Bok Soo finds himself caught up in unexpected situations.