Messiah: Isekai o Sukutta Moto Yuusha

The "former" savior, Takeru Yamato, was summoned to another world and executed because of his strength. When he wakes up, he finds himself in Japan, where he spent time before being summoned. However, in the city, demons appearing from "gates" rampage, and those called hunters fight using magic. Returning from another world, Takeru decides to hide his powers and live, but... Manga original, the current ongoing Web Novel was started by the author based on the manga after it was published, as an alternative read to it as explained by the author in both WN description and Manga advertisement post in Kakuyomu