The Saiyan of Luna Nova

One year after sacrificing himself against Cell, Goku has been living in peace on Other World. He's able to fight strong opponents, and watch over his loved ones whenever he pleases. However, Goku suddenly experiences a change in his life when Grand Kai enlists him as the new guardian of a school for witches called Luna Nova Academy. And there, Goku will meet a familiar face from his childhood.

Note: This is a remake of a one-chapter story called The Protector of Luna Nova Academy. It can be found on Fanfiction.net.