In the middle of the Muromachi period, Satomi Yoshizane, lord of the province of Awa, was attacked by Anzai Kagetsura of the neighboring province. His castle was surrounded, his food ran out, and it was on the verge of falling.
Cornered, Yoshizane said in jest to his dog Yatsufusa, "If you bring me the head of the enemy commander, Anzai Kagetsura, I will give you my daughter, Princess Fuse, as your wife."
That night Yatsufusa slipped out of the castle, crept into the enemy camp, and actually came back with Kagetsura's head in his jaws. Without their commander the Anzai army collapsed, and the Satomi clan was saved.
Yatsufusa demanded Princess Fuse, as promised. Yoshizane, saying he could not give his daughter to a dog, tried to kill Yatsufusa, but Princess Fuse said, "A ruler's word must not be false," and of her own will followed Yatsufusa deep into Mount Tomi in Awa.
The princess lived with Yatsufusa in a mountain cave, spending her days reciting the Lotus Sutra. Softened by her chanting, Yatsufusa never tried to touch her.
But one day, more than a year later, the princess realized she was with child. She had conceived by receiving Yatsufusa's spirit. Just then Kanamari Daisuke, her betrothed, came into the mountains to rescue her and shot Yatsufusa dead with a musket. But the bullet struck the princess too.
To prove her purity, Princess Fuse cut open her belly with a dagger. From the wound rose a white vapor that wrapped around the prayer beads she wore. Eight large beads on the string, marked with the characters for benevolence, righteousness, courtesy, wisdom, loyalty, faith, filial piety and brotherly love, gave off light, flew up into the sky and scattered in all eight directions.
The eight young men born holding these eight jewels are the "eight dog warriors." Kanamari Daisuke became a monk, took the name Chudai Hoshi, and set off on a journey to search for them.