Boushoku-Hi no Ken

Dean is a low-ranked explorer who finds himself surrounded by demonic monsters in a dangerous maze. As he flees, he encounters a powerful demon who consumes strength and discovers the sword Belzera, destined for the Gluttony Empress Belzebuth. The sword gives Dean sudden power, and he sets out to become the first-rate adventurer he has always looked up to. With his new weapon, he ventures deeper into the maze, though what awaits him remains uncertain.