"Summoners" call forth otherworldly, deformed powers through rings. A Summoner’s ability is determined by bloodline, and the protagonist, a boy named Minato Minase, comes from a common family and cannot summon any phantom beasts. On the other hand, his childhood friend, Yukimi Touno, is an elite genius who commands powerful phantom beasts. The gap in their talents only continues to widen. Still, in order to stand beside his childhood friend once again, he continues his reckless training using a sword. One day, Minato and Yukimi fall into a desperate crisis during a small-scale subjugation. The moment he prepares for death, a mysterious woman named Azami appears from his shattered, beloved sword! "I will lend you my power. The price is――" In exchange for overwhelming power, the "price of the contract" that the mysterious woman Azami demands from Minato is not something like his life or heart, but an unprecedented and completely unexpected demand…!?