Kansen Ball Buster is split into two different scenarios titled "The Other Aspect" and "The Chronicle Teller."

"The Other Aspect" features Senoo Kazumi who is currently living alone and job hunting in Tokyo. One day his sister Tsugumi comes to visit him to make sure that he is still alive, since he has not spoken to his family in a while. On the same day, the virus known as Unknown LV4 breaks out causing panic and mayhem across the city. Kazumi becomes determined to save both his sister and his childhood friend Shizuka from their summer camp at the all girl private school. Will he , his sister, and his childhood friend make it to safety in the city or become just another infected individual wandering the city in search of prey?

"The Chronicle Teller" is a collection of 10 - 20 scenes from each of the first five Kansen games. It also explains how each outbreak started, some explanation of the different virus mutations, and a little bit of background information for each of the first five games in the Kansen series.