Renei thinks she´s going crazy. After many years, she has begun to dream about Coo's World all the time, a place beneath the shadow of the mysterious Mount Babiranma, inhabited by fantastic creatures: Nagizari, God, the little Rey, the lethal teppas. Her dead brother, who is going through an identity crisis, may be there, as well as her best friend, who committed suicide some time ago and has now returned for her.

As she muses on making sense of life, things in the real world do not seem to be going her way either. When the inhabitants of Coo's World begin to reveal themselves to her and try to persuade her to go along with them, she no longer knows if her life is a dream or a nightmare. Will they find the answer to the mystery Mt. Babiranma conceals? And more importantly, will they all escape with their lives?