It tells the story of Noir Kuilefth, a 12-year-old boy who has lost his memory. The only thing the boy can know is... He woke up on the last floor of something once referred to as [Dungeon]. There, Noir meets a woman who calls herself as Noir's Mother. Noir's mother tells Noir about many things, and also gives Noir a Mission. That is, a mission to save the world.  What will await Noir on his way to save the world? This is a story about Noir's journey in a world that has lost many of its lives! He will meet all kinds of people, monsters, and even gods.  Will he succeed in his mission?