During the Tokugawa shogunate period, there was a killer named Manji in Edo Castle who was responsible for hundreds of lives. He has infinite life and an immortal body, and has sworn to kill thousands of evil people thousands of times in order to atone for his sins. The leader of the Yida style, Tianjin Yingjiu, who believed that "only victory is the king of the sword", brutally murdered the parents of the sixteen-year-old girl Rin. In order to avenge the bloodshed, she sought out tens of thousands of people as her bodyguards to eliminate the "Yitou Ryu". The story tells that in 1792 when Japan was still in the Edo period, Manji killed his evil corrupt boss and accidentally killed his brother-in-law who came to hunt him down while escaping. Although he wanted to put down the butcher knife ten thousand times, he was constantly hunted and killed, and his sister's life was ruined. Wanci, a swordsman who became immortal due to being buried in blood fairy bugs by eight hundred bhikkhunis, vowed to kill a thousand evil people to atone for the crime of killing a hundred people in order to break the immortal spell caused by the blood fairy bugs. After meeting Rin, an orphan girl with a blood feud, he decided to help her get revenge. Along the way, he encounters Rin's enemy "Itto-ryu", the shogunate's secret agent "Mukai-ryu" who aims to destroy the Itto-ryu, and various other forces or individuals. In Rin's journey of revenge, who could not define right and wrong, Manci defeated powerful opponents one after another - perhaps for him, the realization of the Thousand Man Kill was only a matter of time. However, swordsmen are all people with blood on their hands. Who is kind and who is evil. Does Wan Ci have the qualifications and ability to judge? Murder is a sin, and killing evil people is also murder. Are there really sins in this world that can be redeemed through murder? Everyone just wields the sword for their own reasons. For Wanci, he made a tragic wish to kill thousands of people in the past with irreparable regrets. Maybe this is just a reason to continue to live with a sword, a reason to continue killing... Maybe, this is not a troubled time - without the flames of the Warring States Period, without the madness of the Restoration, the Tokugawa shogunate is ruling everything peacefully, condescendingly watching the battle between swordsmen, and calculating the power that can be driven step by step. Everything seemed to be under some kind of control.