Mikagura Chimai is a 5th grader at a boarding school. Over summer break she returns home and finds a beautiful doll in her family's storehouse. But, that very same night, she has a nightmare, and afterwards she can no longer move her legs. Then her childhood friend Ryuu, a young boy who can see curses, appears before her. He suddenly declares, "You've been cursed by that doll", and immediately after the two of them are dragged into the world of monsters, the "hidden world"!?