Itsuki Isshiki has just graduated from junior high school. He has no parents and no relatives. As the eldest son of six siblings, he decides to become a dungeon adventurer to earn a high income and support his family. "I need money for my family. I'd even risk my life for it." An extraordinary talent that allows him to freely manipulate mana, the raw material for magic, and create spells. This power, which is not used in everyday life, awakens in the dungeon, and Isshiki begins to trample on the common sense of the world—? The ultimate magical tale begins, featuring the eldest son who dedicates all his strength to his family!