Yoko Nakajima is class president and an honour student. At home, she is a good daughter, always obedient to her parents. She pleases everyone around her to the extent of ignoring herself due to her lack of confidence. She has nightmares daily and a unique hair colour that cause some friction at home and suspicion at school.

On a day like any other at school, a strange man named Keiki appears before her. He kneels and swears allegiance to her, promising to protect her and never leave her side. Thereafter they are pursued and attacked by demon-like beasts. In this mix enters two of her classmates who unfortunately happen to be at the wrong place at the wrong time. To escape the onslaught, Keiki transports them to his world. Unfortunately during the journey they are ambushed and end up seperated from one another.

Now they have to learn how to survive in a new land, one with magic, swords, demon-like beasts and immortals.

There is no Juuni Kokuki manga. This anime is based on text novels written by Fuyumi Ono. It features a complex fantasy world with a rich mythology behind it. The series tells us not only Yoko Nakajima`s story, but also stories about other people who came to live in this world.