Youko Nakajima has always simply wanted to be normal. She follows instructions, earns good grades, serves as class president, and assists her classmates whenever possible—but due to her red hair, she has never felt she belonged. Because of her submissive nature, Youko allows classmates to exploit her, leaving her without anyone she can truly call a friend. However, on an otherwise ordinary day, a man claiming to be from another world bursts into Youko's classroom and bows before her. This elegant blond-haired man, Keiki, asserts that Youko is his master and belongs on the throne of his kingdom. Their initial encounter is abruptly ended when Keiki is pursued by otherworldly creatures known as youma. He manages to escape with Youko into his own realm, but two other classmates—Ikuya Asano and Yuka Sugimoto—are also swept up in the chaos. Unfortunately, their difficulties have only just begun, as the youma attack leaves them separated from Keiki. Alone in this strange new land, these ordinary students must learn to survive on their own or perish.