Shinpei Ajiro returns to his home island of Hitogashima after two years away to attend the funeral of his childhood friend Ushio Kofune. Reuniting with Ushio's younger sister Mio and best friend Sou, he begins to uncover the disturbing truth behind Ushio's death — and the island's ancient legend of the shadow disease. The legend says that anyone who sees a shadow wearing their own face will die. Ushio was said to have seen hers. With shadows of death now closing in on Shinpei and his friends, every decision he makes may open a new door to despair. He cannot stop thinking. He cannot stop deciding. He has three days.