The story follows Mitrof de Vansankai, the overweight third son of a noble family. Considered useless by his father, who saw no ability in Mitrof beyond his appetite for food, he is banished from the family and forced to leave his home.
In search of money to satisfy his appetite, Mitrof becomes an adventurer and enters a dangerous labyrinth, filled with death at every turn. While exploring the labyrinth, Mitrof meets a young elf girl named Grace and they team up by chance.
After defeating a kobold in a fierce battle, the two of them achieve a higher ranking (lvl-up) as living beings, known as “sublimation.” Adding a cursed girl named Canule to their party, the three of them continue to explore the labyrinth together.
As they continue to conquer the labyrinth, they encounter a troll, a creature that should normally only exist in the deepest parts of the labyrinth. However, this particular troll had consumed the guardian of the labyrinth and had become an abnormal individual.
In a desperate situation, Mitrof fights with a rapier, his noble pride shining through as he stands up against the troll in battle.