Luck Franzen

Luck Franzen is an S-rank adventurer who stays behind when monsters attack his party in a dungeon. He returns ten years later, younger, after defeating all the monsters in the cave, and discovers that the world now celebrates him as a hero. He chooses to start over under the name Lock as an F-rank adventurer, joining Ario and Genie while also crossing paths with the B-rank adventurer Sia.