The Hidden Dungeon Only I Can Enter (Manga)

Noir Stardia, lesser son of an even lesser noble, just lost his job. Without a penny to his name, he decides to enroll in the Hero Academy and improve his career prospects. But he'll need to get a lot stronger to pass the entrance exam. So Noir seeks out a hidden dungeon--a legendary labyrinth filled with strange beasts and rare items--where he can train until he's powerful enough to change his fate!