The Infinity Castle war is far from over, and one of its heaviest reveals ties the youngest Hashira to the demon he cannot beat alone. In the next stretch of the story, Upper Rank 1 Kokushibo is confirmed as the direct ancestor of Muichiro Tokito, the Mist Hashira. That single fact reframes Muichiro’s prodigious talent and sets up a clash between two members of the same bloodline.
Quick answer: Kokushibo, once the human swordsman Michikatsu, is Muichiro’s ancestor. He is also the twin brother of Yoriichi Tsugikuni, the strongest Demon Slayer who ever lived, which places Muichiro in the Tsugikuni bloodline.
Note: The details below cover events from Demon Slayer’s final arc.
Kokushibo, Michikatsu, and the twin bond with Yoriichi
Before he became a demon, Kokushibo was a human named Michikatsu. He and Yoriichi Tsugikuni were twin brothers. Yoriichi grew into an invincible Demon Slayer and the creator of Sun Breathing, and he was born with a Demon Slayer Mark. Michikatsu lived in his brother’s shadow, and that constant gap between them filled him with jealousy and resentment.
Unable to learn Sun Breathing, let alone master it, Michikatsu built his own style and named it Moon Breathing to mirror his brother’s. His resentment eventually drove him to abandon his humanity and join Muzan. That descent is what turned him into Upper Rank 1, the most dangerous of Muzan’s remaining underlings. His history is drawn out through glimpses in Chapters 174 and 178 of the manga.
The connection to Muichiro flows through this same Tsugikuni line. It explains why Muichiro rose to Hashira at such a young age and why he became one of the few to reach all of the Corps’ ultimate abilities, including the Bright Red Nichirin, the Transparent World, and his own Demon Slayer Mark.
Moon Breathing and what makes Kokushibo dangerous
Moon Breathing is a style seen nowhere else in the series, and it carries 16 forms. On its own it would already be lethal, but Kokushibo pairs it with Blood Demon Art. That combination pushes the technique past visual flourish and lets him launch real crescent moon slices at his opponents. Anyone who cannot dodge or deflect those crescents is cut down.
Who fights Kokushibo in the Infinity Castle battle
Many fans hoped Tanjiro would face Upper Rank 1, but the fight follows the manga by Koyoharu Gotouge, and Tanjiro is not part of it. Instead, Kokushibo takes on his own descendant, Muichiro, alongside Genya and the pairing of Wind Hashira Sanemi Shinazugawa and Stone Hashira Gyomei Himejima. Deploying several of the strongest Hashira together against a single demon reflects just how far above them Kokushibo sits.
| Combatant | Role in the fight |
|---|---|
| Kokushibo (Upper Rank 1) | Muzan’s strongest underling; Muichiro’s ancestor |
| Muichiro Tokito | Mist Hashira and direct descendant |
| Sanemi Shinazugawa | Wind Hashira |
| Gyomei Himejima | Stone Hashira |
| Genya | Demon Slayer fighting alongside the Hashira |
How Muichiro’s sacrifice brings Kokushibo down
Muichiro is overpowered almost immediately. In a one-on-one against his ancestor, he never had a real chance, and he takes serious injuries early. Even so, his role turns out to be decisive. In Chapter 175, published on September 21, 2019 in Weekly Shonen Jump issue #43, a bleeding Muichiro gathers his last strength and lands one final strike, unlocking the Bright Red Nichirin and driving it through Kokushibo’s torso.
The Bright Red Nichirin burns hot enough to cause severe pain to demons and, more importantly, slows their regeneration. That opening lets Sanemi and Gyomei reach the same Bright Red Nichirin state and deliver the final blow, beheading Kokushibo for good. Both Kokushibo and Muichiro die by the end of the clash, but Muichiro’s sacrifice clears the path for his comrades to push on toward Muzan.
When to expect the reveal on screen
The full backstory, the Yoriichi connection, and the bloodline duel are all set for Demon Slayer: Infinity Castle Part 2, the middle entry of the trilogy. That film does not yet have a confirmed release date, and Ufotable has not locked one in, though it is anticipated for 2027.
The first film, Infinity Castle Part 1 — Akaza’s Return, opened in Japanese theaters on July 18, 2025, and became the most successful anime movie to come out of Japan. It moved to home streaming on Crunchyroll starting July 28, 2026, so the Kokushibo confrontation is the next major beat waiting to be animated as the war inside the Infinity Castle continues.