Becoming a powerful demon's familiar might be the best thing ever. But what's the catch? Rory Soletsa is a 17-year-old in a low-magic dimension. He is a student at a magical academy who is supposed to find a familiar. But he doesn't want something trite. He wants to study magical combat and dreams of finding a familiar that can fight alongside him. When he encounters a shape-shifting demon, he asks if the demon will become his familiar but, instead, the demon captures him as her familiar to enter him in an illegal familiar-fighting tournament. The demon undertakes a three-month-long plan to secretly train Rory. She requires him to improve his physical fitness. She teaches him offensive and defensive magical techniques. They also visit Japan where the demon introduces him to aikido…as a way to get him to recognize that, rather than confronting opponents directly, he should avoid their strengths and turn their strengths against them. Rory has numerous harrowing experiences while registering and qualifying for the tournament. He is humiliated and tormented by demons while being inspected. But, after everything he's suffered for, he finally reaches the tournament. What will happen then?