In a world that runs on RPG-style rules where magic points are the essential currency for any fighter or spellcaster, Lent possesses a rare and valuable Gift. He serves as the designated battery for the up-and-coming adventuring party known as the Skypiercers. His unique ability allows him to loan vast quantities of his own magical energy to his companions, ensuring they never run out of power during a fight. While his allies, Guy, Misa, and Eru, use this borrowed magic to evolve into formidable heroes and raise the party's reputation, Lent remains in a supporting role, his own combat potential stagnant.

As his teammates grow stronger and more famous, they begin to view Lent as a burden. Having used his power to climb the ranks, they decide he has outlived his usefulness and coldly expel him from the group. This betrayal awakens a fierce rage in Lent, but more importantly, it triggers the evolution of his dormant Gift. He discovers a hidden sub-ability that turns the tables entirely: the power of forced collection with revolving payments, or interest. Every spell his former allies cast, every technique they honed using his magic, now comes with a price tag, and Lent is the debt collector.

Furious and determined to reclaim what is rightfully his, Lent joins forces with a new partner, a cute yet mischievous support fairy. Together, they embark on a relentless campaign of magical repossession. Using his evolved power, Lent begins to forcibly extract the loaned magic from the Skypiercers, reclaiming every last scrap of MP with compounding interest. What starts as a quest for revenge quickly turns into a power-up loop; the more magic he repossesses, the stronger he becomes, allowing him to manage and multiply the recovered energy to reach the pinnacle of strength in the world.