Aria follows Kinji to the arcade where he manages to win some plush dolls for her. The next day, Kinji and Aria learn that a schoolbus has been hijacked by the fabled Butei-killer and fitted with a bomb that will explode if it slows down with an armed convertible preventing the passengers from interfering. As the busdriver gets injured when an attempt to stop the convertible is foiled by heat-detection, Aria and Kinji arrive on the scene, taking out the convertible. With the bus slowly running out of gas, Aria finds the bomb on the underside of the bus whilst Kinji finds and destroys the communications sensor. The bomb is disarmed by the sniper ace, Reki, but Aria is injured by another armed vehicle whilst trying to protect Kinji. As she is treated in hospital, she feels disappointed that Kinji didn't meet her expectations.

Field trip has finished. Along the way back to Tokyo, someone had planted a bomb within the bullet train where Kinji and the gang are boarded. Not only the bomb will explode if the train's speed is decreased, but they must increase the speed by 10kph every 3 minutes or it will explode. Even worse, Riko had deduced that the culprit is also inside the train! This mission calls for Kinji, Aria, Riko, Shirayuki and the other Buteis present in the train to disarm the bomb and save the passenger. And they've only got 80 minutes until the bullet train reaches Tokyo.