The film stars Seishiro Kato as Rantaro who is sent to a ninja training school by his parents. During the summer, their teacher is invaded by a group of rival ninjas culminating in a race to ring a bell on top of a mountain.

Shimizu Yuichi is a shy and lonely day laborer looking for love. He aimlessly spends time corresponding with girls via telephone dating services and going on random encounters with girls looking for spending cash. His world is shattered one day when he is involved in the murder of one of his former encounters, the sweet-faced Ishibashi Yoshino who, after being jilted by playboy Masuo Keijo, berates and mocks the troubled loner.

At a time when nations are warring, a sword with mysterious power called "Heaven's Sword" is stolen. The sword is said to give its wielder the power to conquer the world. Various ninja all over Dokutake Castle and beyond also manuevering for this sword of immense power. Rantaro and his classmates are assigned to retrieve the stolen sword, their first real ninja mission.