Long ago, humanity discovered weapons later known as Autoscrolls—and the Oath-Making technology that allows command of them. In modern-day Japan, not only have Autoscrolls become a part of everyday life, but Oath-Making is now a systematized science. When high school student and scroll enthusiast of the Oath Club, Kyouta Yuzuki, gets into an accident after finding a mysterious scroll, his freshly transplanted Oath-Heart turns him into a new being!