The action takes place in the autumn of 1600 near the village of Sekigahara. An important duel took place there, in which the Tokugawa clan emerged victorious. They united the country under one rule and ushered in the Edo period, which lasted for 250 years. It was a time of peace and prosperity. During the battle, Kyo Mibu and Demon-Eyed Kyo, two of the strongest samurai, fought each other. At the most crucial moment, they were engulfed by a meteorite that fell from the sky. Since then, both warriors have disappeared without a trace. Four years later, a girl named Yuya Shiina encountered Kyo Mibu in the forest...