Hassai kara Hajimaru Kamigami no Shito no Tensei Seikatsu

Adelphus, the most powerful sage, was defeated by the Calamity Beast, an enemy of mankind, and was taken to heaven. However, he learns that the beast of evil will return in time, and was reborn as an 8-year-old boy named Will. The tale of the peerless Warriors begins now! (Source: MANGA UP!)