Mokyu

Link: The Doujinshi & Manga Lexicon

Rod is an adventurer whose only skill is the supposedly useless \[Unlock], which lets him open treasure chests. Despite being mocked for it, Rod ventures into a labyrinth to make his dream come true, only to be sent flying to the deepest floor by a teleportation trap. But after an unexpected encounter with a “god” on the lowest floor, Rod’s useless skill glitches out and begins evolving into a cheat-level ability…?! Conquering the Five Great Labyrinths with the weakest skill! The grand opening of a “fastest dungeon conquest” adventure begins now!!