Taitou Shirei is a young fighter who makes a habit of attacking members of the corrupt Imperial Army and stealing their supplies for his village. The time has come for him to have his coming-of-age ceremony, for which his family has called in the monk Ryuukou Mouten. After battling Ryuukou and completing the ceremony, Taitou is given the Kenkaranbu, a supposedly legendary sword.

That night, a mysterious and cruel sorcerer, who introduces himself as Shimei, attacks in order to steal the Kenkaranbu. He tells the legend of the Hokushin-Tenkun, seven warriors who are incarnations of the stars of the Big Dipper. He informs Taitou that he is Hagun, one of the two most powerful of these warriors, who is destined to send the world into chaos. When Shimei threatens Taitou's sister Laila Seiren, Taitou is overcome by anger and the power of his star drives him berserk. Laila manages to calm Tatiou down, but in the pandemonium, Shimei manages to get away along with the sword. Thus starts Taitou's journey with Ryuukou and Laila to retake the Kenkaranbu and discover the meaning of possessing the power of a Hokushin-Tenkun.