Kato Teiichi trained under Kazeno Shoma, lost him to Upper Rank Four, and prepared for the Demon Slayer Corps by rescuing Kobayashi Kanon and surviving Final Selection. After joining the Corps and receiving his custom Nichirin Blade, Teiichi began investigating disappearances in Yamada Town, where another girl vanished despite his patrols.
Teiichi cleared missions in Yamada Town and Aomori City, where he befriended Yoshida Rena and later learned that she and her father had died. After discovering that a demon had stolen Rena’s body and infected him with its Blood Demon Art, Teiichi used himself as bait and faced Lower Rank Three Wakuraba.
Teiichi recovered from killing Wakuraba, became the Wind Hashira, and traveled to Kyushu to take up his post. There, he arrived as Obanai Iguro faced the newly promoted Lower Rank Three, Shokugetsu.
Kanae encountered Upper Rank Two Doma in Mine City, and Teiichi arrived in time to protect her. Teiichi held Doma off until dawn, leaving Kanae and Teiichi alive and prompting Kagaya to call a Hashira Meeting.
Teiichi reunited with Kanae and Shinobu, shared what he knew about Upper Rank Two, and helped the Hashira establish regular training and sparring. After returning home, he investigated disappearances on Shoura Island, uncovered the village chief’s coercion by a demon, and searched underwater for the creature.
After killing the water demon, Teiichi faced judgment for killing criminals and using one as bait, then chose to leave the Corps rather than abandon his beliefs. He traveled for years, reunited with Tengen, and eventually encountered Upper Rank Three Akaza in the snow, where they began to fight.
Teiichi defeated Akaza’s escape attempt only to face Kokushibo, who revealed his past as Michikatsu and challenged him in the mountains. Teiichi awakened the Transparent World and fought on with a broken blade, but Kokushibo’s severed blades kept him from reaching his neck.
Teiichi survived encounters with Kokushibo and Akaza, returned to the Butterfly Mansion, and resumed training while recovering. At the Hashira Meeting, he shared intelligence and combat techniques, then accepted Sanemi’s challenge after the meeting.
Teiichi joined the Hashira Battles, then took Muichiro as his disciple and guided him through training and Final Selection until he developed Mist Breathing. In Kazami Town, Muichiro and Teiichi uncovered the truth about the linked Lower Rank Six demons, and the brothers turned on each other as the confrontation continued.
Teiichi trained Muichiro and advised Tanjiro about Nezuko before Tanjiro, Zenitsu, and Inosuke faced the demons controlling the mountain. The mission ended with Tanjiro confronting Rui and Kanon arriving to help Inosuke against the Spider Father.
Tanjiro and Nezuko were accepted by the Demon Slayer Corps, but their journey aboard the Mugen Train led Akaza to learn Teiichi’s location. Teiichi faced six Upper Ranks at Cape Ashizuri, where Gyomei joined the battle and killed Sekido as Doma summoned a giant Bodhisattva.
Teiichi survived a battle against six Upper Ranks by filling the Infinity Castle with Wind Blades, killing Gyokko and Hantengu before Muzan teleported him away. After recovering, he briefed the Hashira, helped establish new training plans, and began training Inosuke.
Teiichi trained the Corps, helped Nezuko overcome sunlight, and brought Tamayo into the Corps’ research efforts. He then joined Tengen Uzui’s search for his missing wives in the Entertainment District, where Daki’s presence emerged and Zenitsu was placed in a house.
Tanjiro and the others uncovered Daki and Gyutaro’s shared weakness and fought to behead them at the same time. The battle continued as Tengen poisoned and wounded pushed into the fight against both siblings.
Teiichi helped defeat Gyutaro and Daki, then brought Nezuko’s sunlight resistance to Kagaya Ubuyashiki and set out to find a stronger Nichirin Blade. At the Swordsmith Village, he accepted Tetsumoto Homura’s challenge to fight Yoriichi Type Zero and began testing the mechanical doll’s limits.
Teiichi stayed in the Swordsmith Village, helped Mitsuri pursue a stronger blade and pushed her to train without holding back. When he left to investigate possible traces of Doma, he encountered Muzan at a train station and fought him until Muzan escaped to the Infinity Castle.
Teiichi, Kanae, and Nezuko investigated Kuroishi Village’s child sacrifices and discovered that the villagers knowingly sent children to a demon in exchange for good harvests. Teiichi killed the Wood Demon and demanded that the village chief release Delia.
Teiichi and Inosuke defeated a demon that created clones, while Sanemi and Giyu searched the Eternal Paradise Cult’s temple for Doma. Doma reached the Swordsmith Village and attacked, leaving Tengen to hold him off as Mitsuri sought weapons and the villagers were warned to evacuate.
Tengen Uzui and Mitsuri Kanroji fought Doma as he attacked the Swordsmith Village, while Teiichi arrived and turned the battle around. After Doma died at sunrise, Muzan learned through Doma that Nezuko had conquered sunlight and began considering how to seize her.
Teiichi prepared the Hashira and Corps members for Muzan’s final battle while they shared their pasts and trained together. Muzan drew the Corps into the Infinity Castle, where the Hashira faced the Upper Ranks as Teiichi rushed to Kagaya Ubuyashiki.