Maryoku 9999-man: Zen Zokusei Tsukai no Dai Kenja

In 1970, “The Great Sage,” Minato Ichikami, saved the world by destroying the invading “Demon God” and its forces. After this intense battle, Minato Ichikami died. After 50 years, he wakes up in a teenager’s body by the name of Minato Kusanagi! Now, the year is 2022, and our hero is inside a student’s body. What’s more, 50 years of peace has weakened magic severely. However, this peace doesn’t last. As demons start returning, Minato Ichikami, now Minato Kusanagi, vows to protect his new life and face his enemies. Witness the return of The Great Sage in this modern era!(Source: WEBTOON)