Daisuke Kanawa, one of Satomi clan's greatest warriors and the fiance of the Princess, thought killed by Kagetsura, returns after a long journey to Castle Satomi. Learning of his bride-to-be's sad fate, Kanawa journeys into the mountains to kill Yatsufusa. He succeeds, but inadvertently slays Fuse as well. With her final words, Fuse tells Kanawa that he is not to blame for her death, that she has been possessed by the vengeful spirit of Tamazusa, killed years before by Yoshizane, whose machinations have caused the tragedies which have befallen the Satomi clan. She begs Kanawa to somehow save her family from the destruction that has come upon them. With Fuse's death, the chain of eight beads hung from her neck scatter and disappear into the sky.

1463: A year after the death of Princess Fuse, in Ohtsuka village in Musashi territory, Shino Inuzuka was born. Now he is 15, the age of manhood. Shino's father, Bansaku presents him with a famous sword, "Murasame", the heirloom of a noble shogun, Nariuji Ashikaga, entrusted and held in safekeeping by Bansaku. Bansaku, growing old and weary, is uncertain of his ability to continue to protect the sword from the petty warlords who desire its prestige. He invests Shino with the mission of locating Ashikaga and returning the longlost Murasame. Soon after, Bansaku is entrapped in a conspiracy between his local magistrate brother-in-law and a strange, demoniac samurai name Samojiro Aboshi. Bansaku is forced into commission of ritual suicide to protect his honor. Aboshi comes for Shino and the Murasame. Seeking to protect his master, Shino's dog attacks Aboshi and is slaughtered by the samurai. Grieving over the corpses, Shino finds a strange, glowing bead on which the character "Ko" - or "Duty" - is inscribed. The first Dog Warrior has been found.

Shino Inuzuka, the first of the Dog Warriors, escapes with the Murasame sword from the trap set by his uncle, Kamezasa, vowing to avenge his father's death and fulfill his mission of delivering the sword to I Lord A4thileana He in attacked in the woods by the sorcerous "jindai". Abosh! barely escapes with his life. Kamezasa, meanwhile, orders Shino's comrade Sosuke to kill Shino, under the pretense that Shino is threatening Hamaji, the woman they both love and to whom Shino is engaged. Sosuke and Shino finally meet on a boat in the middle of the "Wild" River. As Sosuke is about to attack, Shino's "Ko" bead emerges magically from his robe, matched by a similar bead that emerges from Sosuke's, a bead on which is inscribed . -. Acknowledging, though not understanding some inexplicable bond between themselves, Shino and Sosuke end their fight and decide to join as brothers. Under the influence of Kamezasa, Hamaji's foster parents agree to a marriage between Hamaji and the jindai Aboshi. In love with Shino, Hamaji vows to die before the wedding. Aboshi prevents the suicide, but when Hamaji discovers his demonic nature, he launches a murderous assault. As Hamaji is cornered, a man claiming to be her half brother shows up. His name is Dosetsu Inuyama, the third dog warrior.

Meanwhile, Shino is permitted to see Ashikaga to present the Murasame sword, Somehow however, the sword has been replaced with a fake. The vassals of Ashikaga accuse Shino as an assassin and turn on him, but he escapes into the forest. In frustration, Ashikaga's retainers release a particularly dangerous man imprisoned in Ashikaga's dungeon, on condition he find and return Shino. This is Genpachi Inukai, the fourth dog warrior.

Shino and Genpachi fall into the Tone River after lightning strikes Horyu Tower. They are rescued by Genpachi's old friend, Kobungo Inuta, who runs an inn in a small town nearby. A rowdy youth, who as a young man had killed a man, Kobungo sealed his sword after his father was killed trying to stop one of Kobungo's duels. Genpachi is only slightly injured and recovers quickly, but Shino is suffering from a high fever. Kobungo's brother in law, Fusahachi, tips off the search party about the two fugitives and the inn is surrounded by Koga vigilantes. Grimly, Kobungo finally breaks the seal of his sword. Fusahachi attacks Kobuncio. but kills his wife by accident. Infuriated, Kobunao kills Fusahachi. Strangely, upon death the two corpses transform into dogs. Kobungo hurls Fusahachi's head outside, where the Koga vigilantes believe it to be Shino's and return to Koga. Shino now discovers Genpachi and Kobungo also have beads identical to his own.