Jigoku No Ashita summary:

Ashita, a high schooler who will do anything for love, falls down the stairs after a heartbreak. When he opens his eyes, he finds himself crossing the River Styx in the arms of a beautiful woman. Gently comforted by Gasha, the woman, Ashita agrees to go on a trip to Hell. Then Gasha, the headmaster of a school for demons, decides to enroll Ashita...! His school life of bloodshed begins!