A tale of wandering and vengeance by Hai Itto, a master of the Suio style of swordsmanship and a former official intermediary, wage a one-man war along with his infant son, Daigoro against Yagyu clan.

Daigoro wakes and Itto is gone at the request of Kizaemon to avenge the death of Yoichiro. As a 3-year-old alone, Daigoro is lured to a temple where he meets a pickpocket, Oha and trouble ensues.

While eating at an inn, Itto and Daigoro are visited by Okayo, with blood on her hands from her attacker Bunbematsu, whom she accidentally killed. She is protected by Itto, who refuses to turn her over to Torizo, the brothel manager.

Hatsuuchi Suzuki, an official of the Tateyama Clan's Edo residence, attacked the axe-suke of Oshu, an Orizuke, and was beaten to death in a vicious revenge attack. Ittou, however, arrived a day too late. Itto met Hatsuuchi's children, Aya and Soichiro, who appealed to him for revenge. Itto slays Rikuzo in the gambling hall and kills Asuke.

While receiving a request to assassinate in the Ararenji Temple from Saeki, Itto is shot with a poison arrow by the Ura Yagyuans in the form of Unsui, led by Ishine and sent by Yagyu. Meanwhile, while caring for Itto in a coma, Daigoro meets Saya and Lori, a couple that lost a child and becomes fond of Daigoro while Itto's fate is uncertain.

The heavy rains are causing the rivers to overflow and keeping Daigoro and Itto from moving. While watching children play at the rain shelter, Itto remembers a happy past of his child many years ago.