Shûichi Kagaya, a high school student who has been so far without stories, suddenly becomes able to transform himself into a gigantic "monster" with an extraordinary ability. He thus saves Claire's life stuck in a burning house. But Claire discovers her secret and also that she has the opportunity to sneak, through a zipper, into the mascot embodied by Shuichi. And if Shuichi was not the only one in this case!? What awaits these two high school students now bound by destiny!? Their biggest fight is about to begin!! Let's do only one more... to life, to death!