Yoriichi Type Zero

As Muichiro Tokito spars with the mechanical puppet, Tanjiro studies its face and feels he has seen it somewhere. He asks the young caretaker why the doll has six arms and learns that it was built to mimic a genuine warrior, so the extra limbs were needed to reproduce his motions. Tanjiro presses for details, but the boy can only add that it dates to the Sengoku era. Astonished, Tanjiro reckons the puppet must be over three centuries old yet remains intact. The boy explains that his forebears achieved a level of craftsmanship no one can match today, which accounts for its endurance, and that without his late father he lacks the knowledge to repair it himself. Hearing this, Tanjiro grasps why he guards the key so closely against anyone who might wreck the doll.

The pair watch Muichiro a while longer, and Tanjiro marvels at the Hashira's remarkable ability despite being close in age. Muichiro's crow chimes in to loudly praise its master, calling him a prodigy far beyond Tanjiro and an heir to the lineage of Sun Breathing. Curious about that lineage, Tanjiro asks why Muichiro cannot use Sun Breathing, drawing an angry peck from the bird. Mid-scolding, he suddenly recalls his dream and the swordsman whose face mirrors the doll's. The crow halts and grumbles about the impossible timeline, but the caretaker proposes the memory may have been inherited, comparing it to a smith passing down recollections of blades and techniques. Dismissing the notion as foolishness, the crow is cut off when Tanjiro introduces himself and the boy gives his name as Kotetsu.

A noise interrupts them: Muichiro is smashing portions of the puppet, its armor flying loose. Devastated, Kotetsu flees up a tree and weeps over the ruin. Tanjiro finds him and tries to lift his spirits, insisting he will eventually grow capable enough to mend it, but the boy calls himself too pathetic. Climbing up, Tanjiro flicks him to snap him out of his despair and urges him to keep honing his abilities so that, even if he never fixes the doll, those who come after him will. He likens his own path to Kotetsu's, noting that a person may die before reaching their goal yet leave a foundation for someone else to finish. Cheered, the two vow to work hard side by side. Later, walking through the woods, they meet Muichiro again, who reports the training helped but his sword broke, so he intends to take one of the doll's blades.

• The training doll is revealed to be modeled on an ancient swordsman and over three hundred years old.
• Tanjiro meets and befriends the young smith Kotetsu.
• Tanjiro connects the doll's face to the swordsman from his dream.

This installment is the 103rd chapter, set during the Swordsmith Village Arc and collected in Volume 12. Episode 46 of the anime adapts the chapter.