Densetsu no Ore

Ozma, a former court magician, was executed for saving a girl named Felia. However, he is reborn into the same world, but 300 years later. There, he finds that his former self, instead of being an executed criminal, has become a famous name in history, praised like a god and credited with a number of feats that he has no recollection of. A legendary hero!

(Source: Isekai Comics, translated)