The Girl.Kinji Tōyama is a student at Tokyo Butei High school, where agents known as Butei are trained to become crime fighting detectives/mercenaries. Having missed his bus, Kinji rides his bike to school when to his surprise he is chased by a remote-controlled Segway armed with an Uzi, which informs him that a bomb has been attached to his bike which will explode if he slows down (a nod to the movie Speed), and also threatens to shoot him if he jumps off. Kinji is saved by a mysterious pony-tailed girl named Aria Holmes Kanzaki. The two end up pinned down in a gym storage locker as more Segways appear, Aria fends them off, inadvertently sticking her chest right in Kinji's face. As a result Kinji enters Hysteria Mode and he is able to destroy the Segways as well as counter Aria's outraged attacks almost effortlessly. When Kinji finally arrives at school, he learns that Aria has transferred into his class. Later that day, Aria arrives at Kinji's apartment with her baggage and declares him to be her slave.