Kaidou Eiri, the new transfer student at Seiei Academy, is actually a agent working with a secret anti-terrorist government agency known under the code name "Sakura." His objective in infiltrating the school is to get closer to Shimada Fumikazu, a boy in his class whose older brother is the main suspect in a serial bombing case. He tracks down the truth behind the incidents with the help of his "Messiah," or partner, Mitsumi Haku.