A Dutch scholar, Arashi Gensai, tells his sons, Tobitarou and Ryutaro, that he has invented a new explosive that will be useful for peace. However, a group of people looking to get the new explosive sets fire to the mansion, kidnaps Gensai, and flees. Ryutaro mistakenly believes that his brother Tobitarou has been killed by a mysterious group, and resolves to train in the art of the sword in order to rescue his father, Gensai. However, a year has passed and no trace of his father has been found...