In a world where the threat of the “Shiki” (demons) secretly lurks among humanity, a mysterious organization operates according to the laws of the Reiwu world and the ancient contracts of swords. Ryoma, a 16-year-old boy, lives what appears to be a perfectly ordinary and peaceful life alongside his younger sister, Kokoa. But beneath his calm exterior, brilliant intelligence, and apparent laziness, Ryoma hides a secret blade and a mysterious blue mark near his eye... He is not an ordinary stude