One day, dungeons suddenly appeared. Humans with awakened skills then set out to challenge these dungeons in search of hope and riches. Our protagonist, Saeki, having no skills, is considered incompetent; in order to earn enough money for the treatment of his little sister with an incurable disease, he decides to become an adventurer. Saeki has a secret: in his previous life he was the most powerful mage. Now that he’s been reincarnated, he has to level up to regain his former powers. This is the story of an incompetent mage who will turn the world upside down with his power!