Ittoki Sakuraba is puzzled by the intense protection from his mother, uncle, and childhood friend Kousetsu. However, their vigilance becomes clear when a seemingly innocent date with a schoolmate reveals a sinister plot against him. Saved by his ninja-trained uncle and Kousetsu, Ittoki learns he is the 19th heir of the Iga ninja clan, marked for assassination by their rivals. To survive, he must train at the last ninja academy in Japan, the Kokuten Ninja Academy.