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.

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.