"If a male child is born, I will kill you all."

Uha and Ren, two 7-year-old boys from a village of beggars, want to become the legendary sword that draws forth its blade and defeats monsters.

One day, the two boys rescue a fallen legendary sword user, Aiji, in the forest near their village and bring him back. They plead with him to confirm whether they possess any abilities of the legendary sword themselves.

Aiji agrees to check their abilities on the condition that they become his disciples, and he begins to train Uha and Ren, who awaken the powers of the legendary sword.

Seven years pass, and while Ren is away on an errand, the cursed sword, Habuna, enemies of the legendary sword, comes to the village and kills all the villagers, intending to kill both Aiji and Uha as well...