Satsujin Purgatorium

Takasugi Gen deeply regrets the day he killed his adoptive father. So when he dies at the age of 46, only to find himself transported back in time to several years before the murder, he decides to make a fresh start as a high school student.
Trapped in a world between heaven and hell that nonetheless feels like paradise, Takasugi's fight to regain his family and friends begins!