The gods of the celestial plane, as well as creating "people", also created mysterious structures known as "dungeons". Forests, Caves, Towers and Labyrinths... They come in all shapes and sizes throughout the world, full of countless monsters. On a rainy day, Koto, the lone adventurer, ends up meeting Milly, an adventurer who was expelled by her old team. He intended to ignore her after giving her a potion, but she ends up getting attached to him.