ここは俺に任せて先に行けと言ってから10年がたったら伝説になっていた。

To buy his comrades time to escape the Demon King's onslaught, S-rank mage Luck Lock Franzen stays behind alone with the classic line: leave this to me, go on ahead. Grit and guile let him hold that line not for hours but for ten straight years. He wins, and comes back to a world that has already mourned him as a hero fallen in battle. Unable to reclaim his old life, he starts over undercover as the F-rank adventurer 'Lock'. Based on the light novels.