Tsuguko, Kanao Tsuyuri

The twenty-fifth episode covers Tanjiro's rehabilitation at the Butterfly Mansion, where he works to keep Total Concentration Breathing active even in his sleep. His persistence shames Zenitsu and Inosuke into resuming their own training under Shinobu's prodding. A long flashback fills in the backstory of Kanao Tsuyuri, the apprentice who tests Tanjiro, and the episode closes by cutting away to a distant train where an unseen demon strikes.

Holding the breath

To keep his breathing constant through the night, Tanjiro asks the mansion's three young helpers, Naho, Kiyo, and Sumi, to wake him with carpet beaters whenever he lets the technique slip. As his stamina builds, he begins matching Kanao in full-body drills, startling her. Watching from the sidelines, Zenitsu and Inosuke finally seek out Shinobu, who explains that maintaining the technique all day is what is rapidly raising Tanjiro's endurance. After collapsing on their first attempt, the pair are goaded and encouraged into pressing on.

Kanao's past

Flipping a coin to make a choice, Kanao recalls her childhood in a destitute, abusive home and the emotional numbness that followed. Sold off by her parents, she was taken in by the sisters Shinobu and Kanae Kocho, who bought her freedom and brought her to the mansion. Kanae gave her the coin as a way to decide for herself and told her that love might one day reopen her heart. In the present, after his swords arrive from the irritable smiths Haganezuka and Kanamori, Tanjiro masters the constant technique and bests Kanao courteously. Shinobu clears him for missions but knows nothing of Hinokami Kagura, suggesting he ask the absent Flame Hashira. The night ends with Tanjiro confiding in the sleeping Nezuko, as a three-eyed demon kills a passenger aboard a moving train.

The first eyecatcher reworks an earlier chapter cover. The order of events differs from the manga: on the page Tanjiro triumphs over Kanao before receiving his new blade, whereas the anime has him fall just short until the sword is in hand. The medical check-up and the closing scenes of Nezuko's encouragement and the train attack are anime additions not found in the source.