Yona never expected that escaping her bullies would lead her into an abandoned school building.

Inside, she discovers a mysterious book called Guest Invitation, said to contain the ritual for summoning a ghost.

But once the ritual begins, something goes terribly wrong.

A ghost has been awakened.

And Yona is trapped in the middle of a mystery far darker than she could have imagined.

In a city filled with secrets, only one question remains:

Who will be the ruler?