" Attack power ". It is a supernatural ability that manifests for unknown reasons, whether it is due to a mutation or a new type of virus , and because it occurs most frequently in high school students, those who possess the ability are called ` `school students .'' They cause various frictions in their daily lives, and eventually find themselves with nowhere to go. The place where these people gather is the `` Office School ''. A female student transfers to one of these schools, `` Taketa School .''