One day, Yoshimi Satomi, the castle owner of Takita Castle in the country of Anbo, and his confidant Daisuke Kinba, on the way to hunt wild boars, felt sorry for a small dog that was about to be swallowed by a giant snake like a giant tree, and killed the serpent in a fierce battle and saved the puppy. Yoshimi decided to keep the puppy, naming it Hachibo. Now the Serpent Demon is determined to destroy Takita Castle, while Hachibo defends it with his life. His spirit is split into eight, and eight brave warriors must unite to defeat the demoness snake.

After a salary-man's fiancée attempts suicide, he recounts his gruesome family history which saw generations of his ancestors suffer and sacrifice themselves for the sake of their cruel lords.

A sadistic Daimyo (feudal lord) rapes a woman and murders both her and her husband, but even when one of his own vassals commits suicide to bring attention to the crime, the matter is quickly hushed up. Not only will there be no punishment, but because the Daimyo is the Shogun's younger brother, he will soon be appointed to a high political position from which he could wreak even more havoc. Convinced that the fate of the Shogunate hangs in the balance, a plot is hatched to assassinate the Daimyo. The two most brilliant strategic minds of their generation find themselves pitted against each other; one is tasked to defend a man he despises, and has a small army at his disposal. The other is given a suicide mission, and has 12 brave men. They are the 13 Assassins.

Ryujin Misaki, located at the edge of the Genkai Sea, is known as an isolation ward for leprosy patients. When Saotome, a sword master and guard of the Shogun, hears news of a doctor gone missing, he begins to suspect that things are not what they seem at Ryujin Misaki. Intent on discovering the truth, Saotome launches a private investigation.

In a desperate crisis, Inamaru is plunged into the dark sea by a strike from Tokugawa Ieyasu. Ryutaro desperately tries to rescue Inamaru. However, it's not just Ieyasu who aims for him and the precious treasure of the Unshaken Banner. Various individuals, good and evil alike, are aiming for the foothills of Mount Fuji where the hidden treasure lies.

The long-awaited Hakkenshi arrive at Takita Castle, which is saddened by successive defeats.

2nd film in the Eight Brave Brothers trilogy