In a fantasy world where swords, sorcery, and RPG-style mechanics are the laws of everyday life, magic points are the most precious resource. They are needed to fuel spells, execute techniques, and unleash powerful abilities. The protagonist, Lent, is a young man born with a unique Gift that allows him to loan his own vast reserves of magic points to others. He is a member of a rising adventurer party known as the Skypiercers, and for a long time, his role as a living magic battery made him indispensable to his teammates, who relied on his power to become formidable heroes.

However, once his former companions have grown strong enough on the magic he lent them, they begin to question his usefulness in battle. Deeming him a burden who has outlived his purpose, they summarily kick Lent out of the party. Furious and feeling deeply betrayed by their ingratitude, Lent is left to wander on his own until he stumbles upon a new, hidden aspect of his Gift. He discovers that he can now forcibly repossess the magic he loaned out, complete with high interest. Teaming up with an adorably devious and mischievous support fairy, Lent decides to use this newfound power to track down his former party members and extract every last scrap of magic they borrowed from him.

The story follows Lent as he transforms from a discarded support mage into a terrifying and relentless debt collector. The narrative arcs are driven by his methodical campaign of magical repossession against each member of the Skypiercers, with the fairy partner acting as both a guide and a source of cunning strategies. As he repossesses vast amounts of magic, he begins to hoard and invest the reclaimed power, using it to grow stronger than he ever was before, aiming to become the strongest adventurer in the world while getting his revenge on those who wronged him. The manga combines action and fantasy with a comedic, contractual twist on the classic party betrayal premise, proving that when it comes to magic, everything comes with strings attached.