I Became a Legend After My 10 Year-Long Last Stand

Koko wa Ore ni Makasete Saki ni Ike to Ittekara 10-nen ga Tattara Densetsu ni Natteita.

Luck, an S-rank mage in the hero's party, makes a last stand against the Demon King to save his companions. When he finally returns victorious, ten years have passed, and the world praises him as a legendary hero who died in battle. Unable to reclaim his former life, Luck conceals his identity and begins again as "Lock," an F-rank adventurer forging a future in a world that moved on without him.