One day monsters appear in Kakyou City. The school Chiyoko and Haruka are in shakes like during an earthquake and the window panes shatter all at once. During the commotion, the two rush to the rooftop. They see bodies lying in the street and smoke in the distance.

A strange talking cat approaches them and asks them to become 'warriors' in order to fight against 'Biomonsters'. Panicked, Chiyoko is first to agree. She receives a round gemstone-looking transformation device along with a rather painful needle in the back. She suddenly finds herself able to travel faster than the speed of sound. Together with Haruka they are barely able to fend off the Biomonsters.

The cat tells Chiyoko and Haruka they have to search for more students with the potential to become 'warriors' like them. Over the next few weeks they continue searching for members, however, Chiyoko's reputation as a dangerous person and her lack of common sense causes her to be misunderstood frequently. Beyond that, not everyone isn't so willing to risk their life. Why should they be? This isn't the army. No-one is there to force them to join, or to keep order.

Some reach out to others. Some reach out to their friends anew. Others sit back and watch anxiously or with disapproval. Even as the threat of annihilation grows, their personal worries remain in the air.

The days ahead lay filled with turmoil, large and small.