Chapter Summaries

Xia Xi uncovered a blood-written note revealing that Ubagabi had tortured and killed her daughter, Sae, then confronted the demon in her mansion. After his first slash failed to kill her, Ubagabi transformed the rooms with her Blood Demon Art, and Xia Xi assessed her strength.

• Xia Xi found Crimson Red Iron Sand in a drawer and pulled out a blood-covered note describing a child’s abuse and repeated pleas for help.
• Ubagabi appeared and denied framing her husband, claiming he had gambled away the family’s money and beaten her in front of Sae.
• Xia Xi pieced together that Ubagabi had poisoned and tortured Sae to keep her dependent, then killed her after Sae tried to escape.
• Ubagabi revealed that she became a demon after Sae’s funeral and insisted that Xia Xi call her Ubagabi.
• Xia Xi slashed Ubagabi and the door behind her, but her body rejoined as the surrounding rooms transformed into writhing flesh.
• Xia Xi checked the system label identifying Ubagabi as Lower Rank One, the strongest Lower Rank, and a Wind Hashira Killer with the Blood Demon Art Scent of Illusion.

Xia Xi defeated Ubagabi by overwhelming her with a powerful slash, then used a crimson iron-sand device to block Muzan’s communications and interrogated her for intelligence on the Twelve Kizuki. He learned about the Upper and Lower Ranks, but realized Ubagabi’s information was outdated and that he would need to update the current roster.

• Xia Xi cut through Ubagabi’s illusion and flesh-walled room with a single Dawn Breathing slash, then pinned her down with his Great Tachi.
• Xia Xi fitted Ubagabi with a crimson iron-sand Mind Shielding Device, causing her unstable illusion to dissipate as Sanemi and the others arrived.
• Xia Xi hypnotized and interrogated Ubagabi, who named Muzan and revealed that she had eaten Demon Slayer Corps members and nearly a hundred children.
• Ubagabi described several Upper Ranks and said the former Upper Rank Six had been a brother and sister, while another Upper Rank had recently been killed by Matsushita Shousha.
• Ubagabi shared what she knew of the Lower Ranks, including a white-haired child associated with threads, but Xia Xi recognized that much of her intelligence was out of date.
• Xia Xi concluded that he needed to ask the others about the demons they had killed and bring the current Lower Rank roster up to date.

Outside the old mansion, Xia Xi emerged with the defeated Lower Rank One Ubagabi and explained how the metal mesh over her brain blocked Muzan’s connection. After Tamayo collected Ubagabi’s blood, Xia Xi killed her himself, gained 1,557 proficiency, and left the story considering what to do with his bloodied Nichirin blades.

• Yushiro worried that Xia Xi had been hurt, but Tamayo trusted he would survive.
• Xia Xi came out of the mansion dragging the mutilated Ubagabi, while Sanemi, Persimmon, and Yan Zi followed.
• Xia Xi explained that the metal mesh blocked Muzan from monitoring Ubagabi and said he needed to question her before Muzan could make her kill herself.
• Tamayo collected Ubagabi’s blood samples and declined the remaining body tissue, allowing Xia Xi to kill her.
• Xia Xi beheaded Ubagabi with a Bright Red Nichirin Blade, gained 1,557 proficiency in Dawn Breathing, and wondered whether the bloodied blades could still be used for anything else.

Xia Xi struggled to unlock the third Supreme Territory and, with Tamayo’s help, began investigating Yoriichi’s unusual abilities and Muzan’s connection to them. Tamayo recalled that Yoriichi had other traits unlike anyone else, leaving Xia Xi with a possible lead.

• Tamayo resumed her research into Muzan’s bloodline using the powerful Lower Rank blood Xia Xi had provided, while Xia Xi sent Persimmon and Yan Zi ahead and warned them to keep Tamayo’s existence secret.
• Xia Xi trained to unlock the third Supreme Territory, testing hypnosis, willpower, meditation, and other methods, but made no progress.
• Tamayo suggested Xia Xi seek guidance from Yoriichi’s example, and Xia Xi reasoned that Yoriichi must have mastered the Bright Red Nichirin Blade, Transparent World, and a third ability.
• Xia Xi dismissed Yoriichi’s Demon Slayer Mark as the likely third ability and asked whether Muzan had changed after fighting Yoriichi.
• Tamayo recalled that Yoriichi had other traits that set him apart from everyone else.

Xia Xi questioned Tamayo about Muzan’s origins and learned that an ordinary doctor’s herbal medicine had transformed him into a demon. Connecting that impossible achievement with Yoriichi’s mastery of the sword, Xia Xi concluded that the Supreme Territory of the heart was Miracle.

• Tamayo described Yoriichi’s calm demeanor and how Muzan’s defeat left him fearful and changed.
• Xia Xi asked about Muzan’s past, and Tamayo explained that he had been a sickly human from the Ubuyashiki Family.
• Tamayo said Muzan killed the doctor treating him, then the doctor’s herbal medicine cured his illness while turning him into a demon vulnerable to sunlight.
• Xia Xi questioned whether medicine could create beings beyond the demon species, leaving Tamayo reconsidering the limits of her research.
• Remembering Yoriichi’s words about pursuing the Way, Xia Xi declared that the Supreme Territory of the heart was Miracle.

Xia Xi and Tamayo discussed how will could create miracles and learned that Muzan had spent centuries searching for the Blue Spider Lily to overcome his weakness to sunlight. Xia Xi recognized the flower from a graveyard and promised to look for it under the code name “Blue Archive.”

• Xia Xi theorized that extraordinary will could create miracles, and Tamayo wondered whether her medicine might someday achieve one of its own.
• Tamayo explained that Muzan wanted to overcome sunlight and had searched for the Blue Spider Lily, the missing ingredient in the doctor’s prescription.
• Xia Xi remembered seeing a Blue Spider Lily among weeds at a graveyard he had visited with Tanjuro.
• Tamayo warned Xia Xi not to reveal the flower’s location because Muzan would pursue it if he learned about it.
• Xia Xi agreed to search for the flower and bring Tamayo samples, calling it “Blue Archive” to keep its identity secret.

Xia Xi searched the mountain near Yoriichi and his wife’s graves for the Blue Spider Lily but found none, then visited the graves and flew to Tokyo to ask Tanjuro and Kie about the flower. At Tanjuro’s home, Tanjuro and Nezuko sensed something arrive outside.

• Xia Xi left Tamayo’s cottage and flew to the mountain near Okutama to search for the Blue Spider Lily.
• Xia Xi searched the nearby peaks without finding the flower and decided to return next spring with Tamayo or the Butterfly Mansion sisters.
• Xia Xi cleared Yoriichi and his wife’s graves, left offerings, and talked about Yoriichi and Kokushibo while asking for help unlocking the Supreme Territory.
• Xia Xi flew toward Tokyo to ask Tanjuro and Kie about the Blue Spider Lily.
• At Tanjuro’s home, Kie reflected on their improved life in Tokyo as Tanjiro admired his father’s new uniform.
• Tanjuro and Nezuko looked toward the ceiling, sensing something arrive outside.

Xia Xi visited the Kamado family and asked about the Blue Spider Lily, the rare flower Muzan had been seeking. Kie explained how briefly and inconspicuously it bloomed, leaving Xia Xi with a likely reason for why Muzan had never found it.

• Tanjiro and Nezuko sensed Xia Xi approaching, and the family welcomed him into their home.
• Xia Xi saw that Tanjuro had recovered and become powerful, and he noted Tanjiro and Nezuko’s growing skills.
• Xia Xi asked Tanjuro and Kie whether they knew where Blue Spider Lilies grew near their old home.
• Kie explained that the flowers bloomed once a year for only a short time and were difficult to distinguish from weeds.
• Xia Xi concluded that the flowers’ brief blooming window explained Muzan’s failure to find them and told the Kamado family they could boost virility.

Xia Xi arranged to take Tanjuro to a Tokyo hospital and Tamayo for further treatment and research into his congenital Demon Slayer Mark. Meanwhile, Muzan summoned Susamaru and Yahaba and offered them his blood, ordering them to become the new Lower Ranks.

• Xia Xi checked Tanjuro and confirmed that his health had improved through the tailored breathing technique, medicine, and restrained lifestyle.
• Xia Xi told Kie he would take Tanjuro to Tokyo for a lung lavage and to meet Tamayo, while Tanjiro noticed that Xia Xi was hiding something.
• Xia Xi considered having Tamayo investigate whether the Demon Slayer Mark’s lifespan cost could be controlled or replenished.
• Susamaru and Yahaba reunited at Muzan’s mansion, where Yahaba redirected Susamaru’s temari before it struck a mural.
• Muzan explained that the Lower Ranks had disappointed him and offered Susamaru and Yahaba his blood as a chance to become the new Lower Ranks.

Muzan gave Susamaru and Yahaba enough of his blood to promote them to Lower Ranks Five and Six, then reflected on the vacancies among the Twelve Kizuki. Meanwhile, Xia Xi took a recovering Tanjuro from Tokyo toward Tamayo’s courtyard, leaving Kokushibo’s search for Matsushita Shousha unlikely to succeed.

• Muzan forced Susamaru and Yahaba to consume his blood, and their strength increased until they became Lower Rank Five and Lower Rank Six.
• Yahaba used his Blood Demon Art to carry himself and the still-suffering Susamaru out through Muzan’s window.
• Muzan concealed the demons’ visit from his human wife, then recalled Ubagabi’s death and considered the vacant Lower Rank and Upper Rank positions.
• Muzan assessed the remaining Lower Ranks, including Rokuro, Rui, Dark Blade, Xiang Kai, Yahaba, and Susamaru, as potential candidates for advancement.
• Xia Xi traveled with Tanjuro toward Tamayo’s courtyard after System’s medical treatment improved Tanjuro’s condition.

Xia Xi brought Tanjuro to Tamayo so she could study his Demon Slayer Mark and its effects. He revealed that the mark could shorten its bearer's lifespan and might be inherited or spread, then promised to help find a way to prevent that danger.

• Yushiro angrily confronted Xia Xi for bringing Tanjuro to Tamayo's house, and Xia Xi explained that Yushiro was an ally who had never eaten anyone.
• Tamayo mistook Tanjuro for Yoriichi Tsugikuni because of their strong resemblance, and Xia Xi introduced him as a descendant of Yoriichi's friend who practiced Hinokami Kagura.
• Xia Xi told Tamayo that the Blue Spider Lily could not be collected until next spring, but Tanjuro's Demon Slayer Mark could serve as another research subject.
• Xia Xi explained that an awakened Demon Slayer Mark consumed its bearer's lifespan and might spread to other Demon Slayers through prolonged contact.
• Tanjuro worried that his wife, children, and the Swordsmen at the Training Camp might be affected, and Xia Xi said his children's marks would likely stay dormant unless triggered by extreme conditions.
• Xia Xi told Tanjuro that he had brought him to Tamayo to find a way to prevent the marks from shortening their bearers' lives.

Xia Xi and Tamayo investigated how to eliminate the Demon Slayer Mark’s fatal effects, proving that Tanjuro’s blood could trigger the mark under extreme stress while revealing how it rapidly exhausted the body. They began searching for the mark’s cause and for the stabilizing factor in Tanjuro’s blood, which Tamayo named the Steady-Flow Element.

• Tamayo accepted Xia Xi’s theory that Tanjuro’s long life suggested something in his body could resist or alter the Demon Slayer Mark’s effects, and she began researching it with Yushiro and Xia Xi.
• Over the following weeks, Xia Xi’s laboratory skills improved as the researchers studied Tanjuro’s samples, while Tanjuro returned regularly to provide more and Kuang Jin and Sanemi recovered and left for missions.
• Tamayo and Xia Xi injected laboratory animals with fractions of Tanjuro’s blood and found that stress and physical exertion could trigger mark-like patterns in strong subjects exposed to the blood.
• The marked animals temporarily displayed extraordinary strength but died within days, and their mitochondria showed uncontrolled uncoupling proteins that consumed their own resources.
• Xia Xi and Tamayo set out to identify the component that caused the disruption and the stabilizing factor in Tanjuro’s blood, which Xia Xi called the Bloodline Factor and Tamayo named the Steady-Flow Element.

After Suburi reached level five, Xia Xi entered his Mental Core through Sword Zen Meditation and sensed an indistinct voice but could not understand it. Sanemi then delivered a letter from Ubuyashiki warning that Kokushibo was tracking Xia Xi and suggesting he escort Tamayo and Yushiro to a safer location.

• Xia Xi’s Suburi training reached level five, and Sword Zen Meditation drew him into a star-filled Mental Core where he heard an unclear girl’s voice before waking at eight in the morning.
• Xia Xi concluded that Suburi’s upgrade had unlocked this new form of Meditation and that reaching the Mental Core’s center or understanding the voice would take further practice.
• Sanemi returned to Tamayo’s cottage with a letter from Ubuyashiki, after serving as a courier between the Demon Slayer Corps and Tamayo under their secret agreement.
• Xia Xi read reports revealing that Kokushibo had been appearing near Yokohama and tracking the Swordsman Matsushita Shousha, whom the Corps identified as Xia Xi.
• Ubuyashiki warned Xia Xi to move somewhere safer and proposed that he escort Tamayo and Yushiro to a secure area near the Butterfly Mansion.

Xia Xi was asked to persuade the descendants of Michikatsu Tsugikuni after the Demon Slayer Corps discovered their secluded branch. He traced the family’s decline and reached the Tokito family’s home on Mount Kagenobu.

• Tamayo and Yushiro moved their research institute to a safer house near the Butterfly Mansion, with Sanemi and Masachika Kume helping them.
• The Ubuyashiki asked Xia Xi to approach the Tsugikuni descendants after Lady Amane’s attempt to persuade them failed.
• Xia Xi reviewed records showing that Michikatsu left his family, whose fortunes declined over the centuries until its descendants changed their surname.
• The Demon Slayer Corps traced the family through old records, swordsmanship traditions, and antiques sold to pay debts.
• Xia Xi arrived at the descendants’ home and identified them as the Tokito family.

Xia Xi visited the Tokito family to recruit Kiseki Tokito and his sons into the Demon Slayer Corps, but Kiseki initially refused because his wife was ill and he would not leave his family. Xia Xi offered a generous salary and help treating Kiseki’s wife, leaving Yuichiro and Kiseki reconsidering his proposal.

• Muichiro watched ants while Kiseki gathered firewood and medicine for his bedridden wife, and Yuichiro scolded Muichiro for keeping their tired father talking.
• Kiseki heard someone approaching and readied a hoe while Yuichiro and Muichiro guarded the house.
• Xia Xi arrived and said the Demon Slayer Corps had sent him to speak with Kiseki again.
• Kiseki politely refused to join the Corps because his wife was ill and his children needed him.
• Xia Xi offered the family a good learning environment, a generous salary, and medical help for Kiseki’s wife, causing Yuichiro to fall silent.

Xia Xi visited the Tokito family, treated Mrs. Tokito's pneumonia, and explained that he would outline the Demon Slayer Corps' work and benefits before asking Kiseki Tokito to decide whether to join. Kiseki agreed to consider the offer after his wife recovered.

• Xia Xi entered the Tokito home with Kiseki Tokito and Yuichiro Tokito, then introduced himself to Muichiro Tokito as the strongest human swordsman and gave him candy.
• Xia Xi examined Mrs. Tokito and recognized that she had bacterial pneumonia, while Kiseki and Yuichiro hoped he could help her.
• Xia Xi wrote prescriptions and treated Mrs. Tokito, easing her discomfort and steadying her breathing.
• Kiseki Tokito thanked Xia Xi, but hesitated to join the Demon Slayer Corps while his wife was ill.
• Xia Xi offered to explain the Corps' work, compensation, and benefits, and let Kiseki decide after his wife recovered.

Xia Xi explained the Demon Slayer Corps to the Tokitos and treated Kiseki Tokito’s wife, then urged the family to consider joining and blamed their hardships on a curse tied to Michikatsu Tsugikuni. He left Kiseki a Nichirin Blade and a restored copy of the First Generation Moon Breathing, while promising to return in seven days.

• Xia Xi taught Kiseki Tokito how to prepare medicine and care for his wife, promising to continue treating her without using her illness as leverage.
• Xia Xi told Kiseki and the boys that Michikatsu Tsugikuni’s fall to demonhood had cursed their family with misfortune, though Yuichiro challenged his claim as speculation.
• Xia Xi warned that Kiseki might otherwise lose his wife and be left to raise the boys alone, prompting Kiseki and Muichiro to believe him while Yuichiro remained wary.
• Xia Xi gave Kiseki a Nichirin Blade for self-defense and a handwritten copy of the Tsugikuni Swordsmanship, including Michikatsu’s First Generation Moon Breathing.
• Xia Xi encouraged Kiseki to practice the swordsmanship and said he would visit again in seven days.

Kiseki Tokito weighed whether to join the Demon Slayer Corps while Yuichiro tried to protect his family by arguing against becoming swordsmen. Kiseki comforted Yuichiro and brought the brothers to an apology, though he had not yet made his own decision; days later, Xia Xi noticed Yuichiro treated him more kindly.

• Kiseki Tokito went to the nearby Small Town for medicine prescribed by Xia Xi and returned to find Muichiro and Yuichiro at odds.
• Muichiro told Yuichiro he wanted to become a swordsman and help people, but Yuichiro scolded him and insisted their family should live safely as ordinary people.
• Yuichiro told Kiseki he opposed the family becoming swordsmen because they were ordinary and could die fighting demons.
• Kiseki embraced Yuichiro, recognized his fear for his family, and explained that anyone could help others without special talent or status.
• Kiseki asked Yuichiro to apologize to Muichiro, and Yuichiro apologized while maintaining that he had not changed his mind.
• Several days later, Xia Xi returned and was surprised that Yuichiro treated him more kindly.

Xia Xi treated Mrs. Tokito, trained Kiseki and his sons in Moon Breathing, and encouraged Yuichiro to become strong before considering the Demon Slayer Corps. As Mrs. Tokito began recovering, Kiseki went to town for nourishing food and discovered that someone had died in a house there.

• Xia Xi gave Muichiro a mechanical wooden bird, then treated Mrs. Tokito and coached Kiseki, Yuichiro, and Muichiro in Moon Breathing.
• Yuichiro asked whether he could join the Demon Slayer Corps in his father's place, and Xia Xi told him to return after mastering Constant.
• Xia Xi advised Yuichiro to become strong enough to protect the people he cared about, whether or not he joined the Corps.
• The Tokito family followed Xia Xi's instructions, and Mrs. Tokito's weakness and fever gradually improved.
• Kiseki went to town to buy nourishing food for his wife and found a crowd gathered around a house where someone had died.

Kiseki Tokito learned that a neighboring family had been brutally killed and feared demons might be responsible, so he warned his family to stay close and keep their weapons ready. Meanwhile, Xia Xi reached the blazing sun in his inner world and met a little girl who recognized him as her big brother, leaving him stunned when she touched him.

• Kiseki Tokito learned from Officer Kamo that Mr. Miki, his wife, and their two children had been killed by what authorities suspected was a large wild animal.
• Kiseki Tokito returned home shaken, wondered whether demons were behind the killings, and told Yuichiro Tokito and Muichiro Tokito to stay close and carry the short swords Mr. Kurumaji had given them.
• Xia Xi used Hypnosis buffs during Sword Zen Meditation and reached the enormous blazing sun at the center of his inner world.
• Xia Xi touched the sun and descended into a deeper level of consciousness, arriving at a clean Japanese-style residence bearing a scroll signed Kurumaji Masa...
• A blue-tipped-haired girl greeted Xia Xi, touched him, and called him her stupid big brother, shocking him because she seemed to be more than an observer in a cutscene.