Episode 2 of *Demon Slayer: Kimetsu no Yaiba* Season 3 (Swordsmith Village Arc), titled "Yoriichi Type Zero," opens with a tense scene where Muichiro, the Mist Hashira, is seen mercilessly beating up the young swordsmith. Tanjiro, witnessing this act of aggression, steps in with righteous indignation, upset that the Hashira is so callously dismissing the value of the swordsmith's time and contributions. He passionately argues that without the skill and dedication of swordsmiths, Demon Slayers would lack the essential weapons needed to vanquish demons. However, Muichiro, unimpressed and unyielding, simply knocks Tanjiro unconscious and strides away without a second glance.
Meanwhile, Hotaru, lurking nearby in the shadows, overhears Tanjiro's impassioned defense of the swordsmiths. As Tanjiro regains consciousness, Hotaru quickly scurries away, unwilling to confront him just yet. The grateful child swordsmith approaches Tanjiro, thanking him for his intervention, though he laments that he ultimately handed over the key, allowing Muichiro to proceed.
Tanjiro's attention is then drawn to the absence of another Demon Slayer, the one adorned with Hanafuda earrings. The kid informs him that this missing individual is none other than Yoriichi Type Zero, the prototype of an actual Demon Slayer, which requires a specific key to operate. Suddenly, the sound of clashing metal reaches their ears, and they rush to investigate. They arrive just in time to witness Muichiro engaged in a fierce training session with Yoriichi, a formidable automaton boasting six arms. The kid explains that the real Demon Slayer was so extraordinarily skilled that the doll could only hope to mimic his movements with these additional limbs.
As Tanjiro observes the scene, a sense of familiarity washes over him, though he cannot quite place where he has seen the doll before. The kid enlightens him, revealing that the doll hails from the Sengoku period, over three centuries ago, and despite their best efforts, they have been unable to replicate its design. He had been reluctant to surrender the key, fearing that if the doll were to sustain damage, it would be beyond repair.
They watch in awe as Muichiro skillfully battles the doll. Suddenly, Mitsuri's crow swoops in, delivering a surprising revelation: the Mist Hashira is a descendant of a Sun Breathing user. Tanjiro, noticing that Muichiro is not employing the technique, inadvertently voices his observation, prompting the crow to attack him for daring to besmirch its name.
In a flash of insight, Tanjiro recalls the Demon Slayer from his dream. The kid suggests that this could be an inherited memory, speculating that the dream must be a vision of Tanjiro's ancestors. The crow, however, simply cackles at this notion. Grateful for the information, Tanjiro thanks the kid, who then introduces himself as Kotetsu.
At that moment, their attention is diverted by the sight of Muichiro breaking the armor of the doll. Overwhelmed by emotion, Kotetsu bursts into tears and flees, seeking solace in the branches of a nearby tree. Tanjiro follows, offering words of encouragement and inspiration. He urges Kotetsu to channel his grief into motivation, to work hard and become a master swordsmith, thus continuing his family's illustrious legacy, just as Tanjiro is striving to fulfill his own destiny by defeating Muzan.
As Kotetsu's spirits lift, Muichiro nonchalantly passes by them, his indifferent demeanor leaving them both momentarily stunned.
He claims his own sword has shattered, so he's taken the sword belonging to the doll and now brandishes it proudly. The weapon is affixed to one of the doll's severed arms, a testament to its previous battle. Tanjiro observes, noting the absence of malice in the doll's actions—only a cold, indifferent apathy. By the time Kotetsu and Tanjiro stumble upon the doll, it lies broken on the rain-soaked ground. They insert the key, and to their surprise, the doll stirs, though now it moves with only five hands intact.
Fuming with determination, Kotetsu vows to assist Tanjiro in becoming strong enough to defeat the Mist Hashira. The young slayer is taken aback as Kotetsu hurls the doll at him, signaling the immediate commencement of his rigorous training. Over the ensuing days, the doll relentlessly pummels Tanjiro, while Kotetsu alternates between cursing the doll and Tanjiro, urging him to fight with greater vigor. He points out Tanjiro's reliance on habit and emphasizes the need to adapt strategies according to the opponent.
Day after day, Kotetsu berates Tanjiro mercilessly, denying him food and water as part of his harsh regimen. Tanjiro is both amazed by Kotetsu's keen analysis and teaching methods and vexed by his reliance on rainwater for sustenance. One fateful day, he collapses from exhaustion. In his dream, he finds himself submerged underwater, where a glimmering stone catches his eye. Upon awakening, he suddenly gains the ability to anticipate the doll's next move. Though his defense remains feeble, he manages to land a hit, prompting Kotetsu to reward him with food.
Gradually, Tanjiro's senses sharpen, allowing him to discern the direction of the doll's attacks through scent alone. He leaps into action, poised to strike the doll's head, but hesitates, unwilling to damage the doll further. Kotetsu cheers him on, promising to work tirelessly to repair the doll and encouraging Tanjiro to focus on completing his training and delivering the final blow. Just as Tanjiro falls to the ground, exhausted, Kotetsu rushes to his side.
Suddenly, the doll topples over, and to their astonishment, they realize that Tanjiro has indeed sliced off its head. As the head tumbles down, they discover a 300-year-old sword embedded within its body.
In the epilogue, Tanjiro and Nezuko don the masks crafted by the swordsmith. Tanjiro reveals that whispers abound, suggesting Kotetsu's face bears a striking resemblance to the mask he wears. Consequently, many villagers have advised him against donning it. Tanjiro concedes that Kotetsu has a sharp tongue but insists he's a kind-hearted boy beneath his gruff exterior. At that very moment, Kotetsu's voice echoes through the air as he searches for Tanjiro to resume his training, hurling insults as Tanjiro and Nezuko dash away, seeking refuge from the relentless coach.
