Lee Soo-min

Dong-hyun is a high school student. One day, he falls from the rooftop and bumps into Pan-soo who is a passerby. Pan-soo is a member of a criminal organization. When the two men wake up in the hospital, they discover that they have switched bodies. (asianwiki.com)

When a boy falls to his death at school his twin sister, Ok Chan Mi, does not believe that it is suicide. She transfers to Yongtan High, the school in question and meets a witness to her brother's death. When a bully-hunter also shows up at the school, Chan Mi suspects that it may be connected to her brother's death, and looks for this potential ally. (disney+)