Volume 12 is the twelfth volume of Shigurui that includes chapters 60-65.
Iraku ascends swiftly up the social hierarchy while Mie and Fujiki travel to Sunpu. They eventually find shelter at a small cabin, and meet a mysterious stranger with past ties to Iraku.
Iraku is welcomed with great hospitality by Tokugawa Tadanaga and assigned two beautiful female ninja as protection. Meanwhile, Mie visits the local market, but is shunned and charged extortionate prices. Not a single person in a village would speak to her, resulting in Mie walking three miles from Awamoto village to Kakegawa market.
Fujiki and Mie walk to Sunpu, but at a punishing pace for Mie, for Fujiki had not walked with a woman before. Nearing Sunpu and seeking shelter from the train, Fujiki and Mie enter a hut and are greeted by a stranger sitting inside. The stranger asks where are headed, and when told they are headed to Sunpu, he stands and leaves. He was well-built and over 6 feet tall.
Originally, the name Iraku Seigen belonged to a family of physicians. In Edo, in 1616, lived a town doctor named Iraku Seigen. He was a master of Kosshi Jutsu and used acupressure on vital meridians. His treatment had the power to cure even the ailments of internal organs. Although he had been invited to serve as court physician to the daimyo, he dedicated himself to practice in the town for the common people. One day, Iraku Seigen returned to his practice and found his new assistant greeting him. The allure of his eyes, voice and long black hair had a visible effect on Iraku. Iraku Seigen had met the assistant ten days earlier and was hired due to his attractive looks. Since his arrival, the assistant became the talk of the local populace and the clinic became crowded with women. Iraku’s apprentice, Shun'an, the same tall man Fujiki and Mie met inside the hut, was suspicious of the new assistant. The assistant asks Iraku whether the techniques Iraku mastered had the power to grant and take life. Iraku informs his assistant that if one has knowledge of the pressure points, you could lengthen or shorten a person's lifespan. Whereas Iraku used this knowledge for the wellbeing of others, he warned his assistant against using it for harm, for it would surely result in his assistant becoming a demon. He demonstrates this by asking for his assistant’s hand and pressing against his palm with his thumb, which causes his assistant to fall to the floor in agonising pain. The assistant acknowledges the terrifying power of Kosshi Jutsu and asks for more techniques. The seductive allure of the assistant renders Iraku unable to resist. Later, on a small boat on a lake, after the Iraku confirms to his assistant that he has imparted to him all he knew, the assistant embraces Iraku, and then proceeds to murder him using his own fatal techniques against him. According to the testimony of witnesses, it was a homosexual love suicide, and the bodies were not found. With his master dead, Shu'an left the town, barely scraping by on practicing his craft. One day, a Ronin from Enshuu told him of a beautiful black haired swordsman called Iraku Seigen who had made a name for himself and killed his master. In disbelief that the assistant had taken his master's name, Shu'an headed to Sunpu to kill Iraku, not out of revenge, but in the belief that a demon should not be allowed to live.
In order to select an opponent for Iraku. The Chamberlain of Saegusa Takamasa was to watch a match between Fujiki and Shu'an. The Chamberlain is suddenly ordered to the Castle at night. Awaiting him in the chamber is the envoy Mabuchi Gyoubu Nosuke, who informs the Chamberlain real swords will be used. The Chamberlain dismisses the idea, considering the order a metaphorical means to encourage contestants to participate. The Chamberlain asks how the duel went.
Earlier, Tsukioka, now named Hoshikawa, is invited to act as referee to a duel involving wooden swords, though Shu'an declines, instead preferring to use his fists. On hearing this, Fujiki decides to do the same, even though Shu'an was three times his size. Hoshikawa is concerned the difference in size was two great, and therefore not a fair match. However, Fujiki strikes down Shu'an with a single strike, the latter cowering in fear of Fujiki and sensing he too was a demon. Gyoubu proclaims he had no idea what Shu'an saw in that moment. The doctor noted Shun’an later died not from the strike, but that he must have seen something, because lurking in every man's soul was a darkness called Mumyou, also known as Avidya, a Buddhist term for ignorance of spiritual darkness. It is said experts in Kosshi Jutsu have clairvoyant powers, and wondered how much darkness there must exist in Fujiki’s soul to kill Shu'an. Later on his way home, the envoy Gyoubu meets his end falling from his horse.
In a flashback, a young Fujiki, who had just entered the Kogan-ryuu, runs in a back street within the village of Togiya. He kneels outside a house, and calls for Iku. Iku appears, and Fujiki informs her Kogan had sent for her. Iku notices Fujiki was bruised, and like a mother to a child, orders him to wash his mouth. Iku then invites Fujiki inside, and orders him remove his dirty clothes. The Kogan-ryuu was known for its pitiless training, and on one occasion a student sent to Togiya for Iku dropped dead on street due to a punctured lung. Iku carefully checks for broken bones, and rubs Fujuki’s hand with disinfected alcohol. Iku orders Fujiki to eat his full while she mends his torn clothes. Iku notices how little Fujiki spoke, some said it because he lacked feeling. When Iku, the subject of a towns children's song walked along the street with a bruised Fujiki, people scowled. Iku thought, despite his reticence, there was nothing wrong with Fujiki. As they walk, Iku tells Fujiki he would surely be the heir to the Kogan-ryuu, causing Fujiki to blush. Years later and now an adult, Fujiki ran along the same back street. He once again stands outside Iku’s home and informs her she has been sent for, even though the ceremony for the 2nd anniversary of Kogan's wife's death had only just ended. Requesting they make haste, Iku notices Fujiki’s thickly calloused hand. Even though Fujiki closed his eyes as Iku undresses with her back to him, Fujiki feels a strong warmth emanating from her.
In the present day, at Sunpu. Hoshikawa warns Fujiki not to draw his sword when they near the castle for any reason. Meanwhile, at the village of Hasedera, in Hoshikawa’s Toda-ryuu dojo, Iku sits sewing, but walks outside upon hearing the sound of incoming visitors. She observes Hoshikawa escorting Fujiki and Mie. Iku calls out Fujiki’s name in surprise; and Fujiki responds by calling out Iku. The hand which Iku had treated was gone, as was her white back, now replaced with a tattoo of a dragon. As Hoshikawa attempts to explain to Iku why Fujiki and Mie were the accompanying him, Iku witnesses Mie, who suddenly appears as if possessed by a demon. Hoshikawa draws his sword as Mie unsheathes a knife. Fujiki, who a moment earlier called out warmly to Iku, stood in front of Mie and despite Hoshikawa’s earlier warning, draws his sword as if at Mie's will. Hoshikawa pleads with Fujiki to stop.
The even tempered and mild man Hoshikawa had spilled blood five times even in peace time. Though he had no wish to kill, he was forced to under circumstance. He had even left his home town and changed his name to avoid coming across those who bore a grudge against him. Using Mineuchi Fusatsu, Hoshikawa was more afraid of killing than being killed. On completing his Nagare strike, which Hoshikawa skilfully evaded, Fujiki drops his long sword, and as Hoshikawa’s sword strikes down on Fujiki, Fujiki blocks it using the grip of his short sword in the same way he had done against Iraku. With Hoshikawa’s sword embedded into the grip of Fujiki’s sword, Hoshikawa shakes Fujiki’s sword away. Although appearing without a weapon, Hoshikawa’s own short sword had been taken from him by Fujiki and pressed to his neck. Fujiki asks Hoshikawa if he was Iraku’s lackey, and Hoshikawa replies that was ridiculous, for Iraku was the victor, and there was no reason for him to challenge Fujiki. Furthermore, after an officially authorised vengeance match, it was forbidden to seek further retaliation.