Chapter Summaries

Tetsu no Sosuke asked Kotetsu for Yoriichi Type Zero so he could try to repair it and build a new Automaton Puppet. Kotetsu agreed on the condition that Sosuke would not train with it until it was repaired.

• Tetsu no Sosuke told Kotetsu he had come back to find him and ask about Yoriichi Type Zero.
• Kotetsu tried to run away, but Tetsu no Sosuke caught him and lifted him by the collar.
• Tetsu no Sosuke explained that he wanted to repair Yoriichi Type Zero and build a new Automaton Puppet, not train with the damaged one.
• Kotetsu agreed to hand over Yoriichi Type Zero if Tetsu no Sosuke promised not to train with it before repairing it.
• Tetsu no Sosuke accepted Kotetsu's condition and said he had no intention of risking his life with the puppet.

Tetsu no Sosuke saw Yoriichi Type Zero and decided to take it home so he could study how it was made. He left Kotetsu encouraging him to keep training, though Kotetsu doubted his own talent.

• Kotetsu took Tetsu no Sosuke to see Yoriichi Type Zero, and Tetsu no Sosuke admired the puppet as a priceless work of art.
• Tetsu no Sosuke admitted he had no confidence he could recreate the puppet, but decided he could still make a similar one.
• Tetsu no Sosuke carried Yoriichi Type Zero home himself to avoid wearing down its mechanisms.
• Kotetsu was amazed by Tetsu no Sosuke's strength and asked whether training could make him that strong.
• Tetsu no Sosuke told Kotetsu he could improve through training, then rapped him on the head when Kotetsu said he lacked talent.

Tetsu no Sosuke encouraged Kotetsu to keep working despite believing he lacked talent, using his own experience as an example. After Kotetsu left to act on the advice, Tetsu no Sosuke turned his attention to understanding the Automaton Puppet so he could build another one for himself and the Demon Slayer Corps.

• Tetsu no Sosuke reminded Kotetsu that he had also once been considered untalented and explained how persistence had helped him improve at forging.
• Tetsu no Sosuke urged Kotetsu to focus on what he could do and keep practicing until he succeeded.
• Kotetsu accepted the advice and left to get to work.
• Tetsu no Sosuke reflected that he could make the most of his strengths by perfecting a single sword swing.
• Tetsu no Sosuke set out to study the Automaton Puppet and build a new one.

Tetsu no Sosuke began taking apart Yoriichi Type Zero to study its construction and hoped to retrieve the sword inside it. Kotetsu returned after deciding to train, then found Tetsu no Sosuke holding the puppet’s detached arm and rushed to confront him.

• Tetsu no Sosuke decided to document Yoriichi Type Zero before disassembling it so he could put it back together correctly.
• Tetsu no Sosuke recalled the sword inside the puppet and began dismantling one arm after drawing its structure.
• Kotetsu accepted Tetsu no Sosuke’s advice and exercised until he was exhausted.
• Kotetsu hurried back to check on Yoriichi Type Zero and saw Tetsu no Sosuke examining its detached arm.
• Kotetsu charged at Tetsu no Sosuke, demanding to know what he had done.

Tetsu no Sosuke dismantled the Automaton Puppet to study how its arm worked and record its measurements. After confirming that it still functioned, he examined a joint mechanism and explained the challenges of making the puppet perform sword techniques.

• Tetsu no Sosuke stopped Kotetsu from interfering and began measuring and documenting the puppet's parts.
• Tetsu no Sosuke removed and reattached several fingers, then put the arm back together.
• Kotetsu activated the Automaton Puppet and saw its six arms move, confirming it still worked.
• Kotetsu noticed Tetsu no Sosuke's diagrams of the puppet's components and watched him dismantle an arm completely.
• Tetsu no Sosuke showed Kotetsu a tiny steel ball in the puppet's joint and described the difficulty of controlling its movements and sword techniques.

Tetsu no Sosuke studied the Automaton Puppet's Metal Skeleton and began building a replacement arm, balancing his work with daily Swordsmanship practice. After seven days, his second attempt worked smoothly, and he moved on to the other arm.

• Tetsu no Sosuke spent the night taking apart and reassembling the Metal Skeleton while Kotetsu waited beside him and fell asleep.
• Tetsu no Sosuke decided to make one arm first, then revise his work based on whether it succeeded or failed.
• Tetsu no Sosuke made components for the Automaton Puppet each morning and practiced Swordsmanship each afternoon, while explaining his work to Kotetsu.
• Tetsu no Sosuke built a first arm that moved poorly, then redesigned it after watching the Automaton Puppet's movements.
• Kotetsu activated the Automaton Puppet, and Tetsu no Sosuke saw that his second arm worked smoothly before starting on the other arm.

Tetsu no Sosuke reunited with Kanae and Shinobu Kocho at the Swordsmith Village while working on Yoriichi Type Zero. He explained his plans for the puppet and regretted that the Breathing Technique he taught the three swordsmiths had exhausted them.

• Tetsu no Sosuke stopped Kotetsu from jumping at the puppet, then spotted Kanae and Shinobu Kocho approaching.
• Tetsu no Sosuke greeted Kanae affectionately, and Kanae explained that she and Shinobu had come after receiving his letter.
• Tetsu no Sosuke described his plans to repair Yoriichi Type Zero and build puppets to help patients and Demon Slayer Corps members train.
• Shinobu Kocho confronted Tetsu no Sosuke about the Breathing Technique that had left the three swordsmiths drained.
• Tetsu no Sosuke admitted he had not thought things through, and Kanae said the technique had likely been too difficult for their bodies.

Tetsu no Sosuke and Kanae discussed how to make the Swordsmiths’ use of Sunblaze less dangerous, but Sosuke set the problem aside because he feared weakening their blades too much. He introduced Kotetsu to the Kocho sisters, then took Kanae into his house for her first visit.

• Tetsu no Sosuke explained that the Swordsmiths could recover after a few days’ rest and wondered whether limiting their Sunblaze use would reduce the strain.
• Kanae suggested combining the hammering method with ordinary techniques and testing how much Sunblaze the Swordsmiths could tolerate.
• Tetsu no Sosuke worried that reducing Sunblaze would leave the Nichirin Blades too weak, so he postponed the idea.
• Tetsu no Sosuke introduced Kotetsu to Kanae and Shinobu Kocho, and Kotetsu teased Kanae by asking if she was Sosuke’s wife.
• Shinobu Kocho punished Kotetsu for his remarks while Tetsu no Sosuke took Kanae by the hand and headed inside.
• Kanae entered Tetsu no Sosuke’s house for the first time.

Kanae visited Tetsu no Sosuke, who was working on the Automaton Puppet and expected to be away for some time. Before Kanae returned to the Butterfly Estate, he checked her Nichirin Blade and told her to bring it to him if it was damaged.

• Tetsu no Sosuke brought Kanae rice balls, and she admitted she had missed both them and him.
• Shinobu Kocho teased Kanae, who tossed her outside, where Kotetsu laughed at her.
• Tetsu no Sosuke told Kanae that building the Automaton Puppet was taking longer than expected and that he had spent seven days making one arm.
• Kanae said she could stay for only three days before returning to the Butterfly Estate.
• Tetsu no Sosuke inspected Kanae's Nichirin Blade, confirmed it was undamaged, and told her to come to him if it was ever damaged.
• Kanae called Tetsu no Sosuke handsome.

Tetsu no Sosuke planned to continue rebuilding the Automaton Puppet before returning to the Butterfly Estate, then took Kanae and Shinobu Kocho on a tour of Swordsmith Village. The group climbed into the Mountains and reached a beautiful scenic spot.

• Tetsu no Sosuke told Kanae he would finish studying and rebuilding the Automaton Puppet before returning to the Butterfly Estate.
• Kanae invited Tetsu no Sosuke to train with Kanroji Mitsuri, but he worried she would overpower him and considered seeking training from Iguro Obanai or the Rock Pillar instead.
• Tetsu no Sosuke offered to show Kanae around Swordsmith Village and suggested they soak in the hot springs together that night.
• Tetsu no Sosuke took Kanae and Shinobu Kocho around Swordsmith Village and then led them into the Mountains.
• Tetsu no Sosuke guided Kanae and Shinobu Kocho to a beautiful spot in the Mountains.

Tetsu no Sosuke brought Kanae and Shinobu Kocho to a secluded spring and waterfall, where he and Kanae imagined building a peaceful life together after the demons were defeated. As Shinobu chased Tetsu no Sosuke through the snow, Kanae’s conviction grew stronger.

• Tetsu no Sosuke showed Kanae the spring and waterfall and described how beautiful the place became in spring.
• Tetsu no Sosuke asked Kanae to live with him there someday, and she planned a house, a sword-forging shed, and a small farm.
• Shinobu Kocho caught a plump rabbit, and Tetsu no Sosuke teased her about being a stupid kid.
• Shinobu Kocho chased Tetsu no Sosuke through the snow while Kanae watched and tightened her grip on her Nichirin Blade.

Tetsu no Sosuke trained with the Kocho Sisters before they departed, while Kanae’s growing love for him strengthened her resolve. Back at the Sword Forging Shed, Kotetsu noticed Sosuke’s renewed focus as he worked on the Automaton Puppet and anticipated something unusual.

• The girl reflected on how Tetsu no Sosuke had become part of her life and resolved to strive toward a future with him.
• Tetsu no Sosuke resumed studying the Automaton Puppet in the morning and honing his swordsmanship in the afternoon.
• Shinobu Kocho sparred with Tetsu no Sosuke and found his improved perception and agility made him difficult to pin down.
• After three days, the Kocho Sisters prepared to leave, and Kanae Kocho told Tetsu no Sosuke she would wait for him at home.
• Kotetsu watched Tetsu no Sosuke work on another Automaton Puppet arm and sensed that something was different.

Tetsu no Sosuke worked on repairing the Automaton Puppet while lovesick thoughts about the Flower Pillar distracted him. After studying the puppet’s leg, he decided he could reproduce it, but that evening he questioned whether he should continue the repair at all.

• Tetsu no Sosuke’s lovesick dazes alternated with bursts of intense work, and he completed replicas of all six arms.
• Kotetsu worried that the Flower Pillar’s sister might beat Tetsu no Sosuke, then asked what they should work on next.
• Tetsu no Sosuke removed and examined one of the Automaton Puppet’s legs, drew its mechanisms, and identified balance, direction changes, and precision as the main challenges.
• Tetsu no Sosuke decided to make a leg and test his design, and Kotetsu expected the puppet to be repaired soon.
• That evening, Tetsu no Sosuke wondered whether he should leave the Automaton Puppet alone because he did not need its sword or care who obtained it.

Sanemi Shinazugawa came to the Swordsmith Village to have his damaged Nichirin Blade repaired, but Kawahara Chintetsu and Tetsu no Sosuke asked him to help test an Automaton Puppet. Sanemi reluctantly followed Tetsu no Sosuke into the woods, where the test was about to begin.

• Sanemi Shinazugawa sought Tetsu no Sosuke after a tough Demon damaged his sword, and the Swordsmith Village asked him to visit in person.
• Kawahara Chintetsu told Sanemi that the village needed his help with two things, including a test.
• Tetsu no Sosuke appeared and explained that the test involved an Automaton Puppet, not a Demon.
• Sanemi reluctantly followed Tetsu no Sosuke to a wooded area near his home.

Tetsu no Sosuke brought Sanemi Shinazugawa to test the restored Yoriichi Type Zero, while promising to repair Sanemi’s blade. The test began with Sanemi attacking the puppet, which revealed a dangerous new defense.

• Sanemi Shinazugawa came with Tetsu no Sosuke because he valued the quality of his forged blades.
• Tetsu no Sosuke explained that he had repaired Yoriichi Type Zero and asked Sanemi to test it.
• Tetsu no Sosuke gave Sanemi an ordinary sword, and Kotetsu activated the puppet.
• Sanemi charged the puppet and swung at its neck, but it spun its six blades into a sweeping crescent that threatened to cut him in half.

Tetsu no Sosuke and Kotetsu tested the repaired puppet against Sanemi Shinazugawa and confirmed it could withstand attacks and perform a new sword technique. Sanemi ignored Tetsu no Sosuke’s call to stop and fought until the puppet ran out of power.

• The puppet unleashed a new blade technique, and Sanemi Shinazugawa countered with the Sixth Form of Breath of the Wind.
• Sanemi landed several shallow cuts on his body while the puppet remained intact and charged him again.
• Kotetsu celebrated as Tetsu no Sosuke concluded that the puppet could endure sword strikes and execute new techniques.
• Tetsu no Sosuke called for Sanemi to stop, but Sanemi continued attacking until the puppet ran out of power.

After repairing Sanemi Shinazugawa’s Nichirin Blade, Tetsu no Sosuke prepared to leave the village with him. A Kasugai Crow then ordered them to bring Tetsu no Sosuke to see the master first, leaving his plan to return to the Butterfly Estate on hold.

• Sanemi Shinazugawa sparred with the repaired Automaton Puppet for two days, and neither he nor the puppet suffered serious damage.
• Tetsu no Sosuke returned Sanemi Shinazugawa’s repaired blade and prepared to leave after saying goodbye to Kotetsu.
• Sanemi Shinazugawa learned that the Village Chief’s second request was for him to escort Tetsu no Sosuke, and the two left together.
• After they exited the village under escort and removed their masks, a Kasugai Crow ordered Sanemi Shinazugawa to take Tetsu no Sosuke to see the master.
• Tetsu no Sosuke considered returning to the Butterfly Estate first, while Sanemi Shinazugawa told him to get moving.

Tetsu no Sosuke met with Ubuyashiki Kagaya, who asked about his restoration of the Automaton Puppet. Sosuke proposed making more puppets to train the Demon Slayer Corps and asked to enlist the Hidden’s help.

• Sanemi Shinazugawa escorted Tetsu no Sosuke to the Master’s residence after Sosuke agreed to go.
• Tetsu no Sosuke reunited with Kanae, who said she had been waiting for him and would return with him to the Butterfly Estate.
• Tetsu no Sosuke entered Ubuyashiki Kagaya’s room and learned that Kagaya’s health had worsened.
• Ubuyashiki Kagaya praised Tetsu no Sosuke for restoring the Automaton Puppet and asked how well he understood it.
• Tetsu no Sosuke said he could make puppets of different levels to train Demon Slayer Corps members, though each would take at least a month to build.
• Tetsu no Sosuke asked Ubuyashiki Kagaya for permission to have members of the Hidden help him.

Tetsu no Sosuke offered to let the Hidden make the Automaton Puppet’s outer parts, explaining that he was willing to share the work to help the Demon Slayer Corps. Ubuyashiki Kagaya asked him to visit several former Breathing Technique masters and make training puppets for their successors, leaving Tetsu no Sosuke to decide when to go.

• Tetsu no Sosuke proposed having the Hidden make the Automaton Puppet’s outer parts to reduce production time.
• Ubuyashiki Kagaya warned that sharing the work could expose the puppet’s secrets, but Tetsu no Sosuke said he did not mind sharing knowledge that could help the Corps.
• Tetsu no Sosuke revealed that he had already written down the technique and given it to Kotetsu in the Swordsmith Village.
• Ubuyashiki Kagaya asked Tetsu no Sosuke to visit Urokodaki Sakonji, Kuwajima Jigoro, and Rengoku Shinjuro to develop training puppets based on their Breathing Techniques and Swordsmanship.
• Ubuyashiki Kagaya said he would write to the masters and let Tetsu no Sosuke choose when to leave.

Tetsu no Sosuke left Ubuyashiki Kagaya’s residence with Kanae, thinking about how to train the former Pillars and seek their Swordsmanship guidance. On the quiet walk home, he and Kanae agreed they could simply look at each other all day.

• Tetsu no Sosuke told Ubuyashiki Kagaya he would leave as soon as he could, and Ubuyashiki Kagaya dismissed him.
• Tetsu no Sosuke took Kanae’s hand and left, while Sanemi Shinazugawa went inside after Ubuyashiki Kagaya called him.
• Tetsu no Sosuke considered making Automaton Puppets to train the former Pillars and asking them for Swordsmanship guidance.
• Kanae told Tetsu no Sosuke she liked looking at him, and they agreed to keep looking at each other instead of sneaking glances.