17th year of the Kan’ei era (1640). The echoes of the Warring States period had yet to die out; rounin still roamed the land in search of employment and food, while even among the shogun’s own retainers swordsmen prowled the streets cutting down passersby without cause. In that forsaken world reeking of death, a mysterious swordsman wanders. His name — Futatsukage Sougen. A swordsman with two shadows. The shadow torn in two marks him as a cursed being. One shadow belongs to a human, the other to something inhuman. Because of this duality, he is hunted from both the living world and the underworld, and thus the path he walks is strewn with flesh and bloodied vomit. Perhaps because of his cursed blood—or by sheer coincidence—Sougen finds himself drawn to a terrifying island that mirrors his own curse - Awahomurajima. This is an island sharing the name of the formless, uncanny island mentioned in the Kojiki, and it harbors bizarre, inexplicable phenomena. An island where every child born is a twin. An island where one of each twin is inevitably sacrificed. An island filled with torii gates corresponding to the number of children born. What cursed rituals are performed there? Can the swordsman with two shadows break his own curse? And will he manage to leave this cursed island alive? A full-fledged historical fantasy. Drawing inspiration from numerous classical Japanese fantastic tales, the story begins here!