Who Is Kokushibo? Demon Slayer’s Upper Moon One Explained

2025-07-23

In the dark and tragic world of Demon Slayer: Kimetsu no Yaiba, few characters evoke as much awe and fear as Kokushibo.

Known as Upper Moon One, Kokushibo stands at the pinnacle of Muzan Kibutsuji’s demon hierarchy, making him the most powerful demon aside from Muzan himself.

His chilling presence, mysterious backstory, and breathtaking battles have left fans deeply intrigued. But who exactly is Kokushibo? Let’s explore his origins, powers, and defining moments in Demon Slayer.

Kokushibo’s Origin: From Human Samurai to Demon

Before he became Kokushibo, he was Michikatsu Tsugikuni, a renowned samurai from Japan’s Sengoku era.

Born during the same time as his younger twin brother Yoriichi Tsugikuni, the creator of Sun Breathing, Michikatsu lived under his brother’s shadow.

Yoriichi was born with the Demon Slayer Mark and extraordinary talent—so much so that even as a child, he was capable of defeating adult swordsmen and, later, even demons with ease.

Despite Michikatsu’s own strength and skills, he felt inferior and jealous of Yoriichi’s natural gifts. Eventually, in pursuit of power and longevity, Michikatsu succumbed to temptation and accepted Muzan’s offer to become a demon, thus becoming Kokushibo.

His transformation into a demon preserved his fighting prowess and granted him immense power, but it also marked his descent into darkness and internal torment.

Breathing Style and Powers: Moon Breathing

What makes Kokushibo especially unique among demons is that he retains his Breathing Style even after becoming a demon.

Unlike other demons who rely solely on Blood Demon Arts, Kokushibo uses Moon Breathing, an offshoot of Sun Breathing that he developed himself.

Key abilities include:

Moon Breathing Forms: Over a dozen forms with wide, chaotic crescent slashes that make it almost impossible for opponents to defend.
Regeneration: As Upper Rank One, his healing is instantaneous—even fatal wounds are ineffective unless his head is severed by a Nichirin blade.
Blood Demon Art: Combined with his swordsmanship, Kokushibo’s flesh katana generates unpredictable and explosive moon-shaped blades.
Enhanced Physicality: Kokushibo surpasses nearly all demons in terms of speed, strength, and perception.

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Kokushibo vs Muichiro, Genya, Sanemi, and Gyomei

One of Kokushibo’s most memorable moments is his brutal final battle in the manga.

When the Demon Slayer Corps' strongest Hashira, Sanemi (Wind) and Gyomei (Stone), join forces with Muichiro (Mist Hashira) and Genya Shinazugawa, readers witness a climactic, high-stakes showdown.

Muichiro inflicts a vital wound that paves the way for his defeat.
Genya uses demon-enhanced body abilities to stall Kokushibo.
Sanemi and Gyomei match him blow for blow with their impeccable coordination and brute strength.

In a rare moment of clarity, Kokushibo sees his reflection in death—not as a proud warrior but as a twisted echo of his former self, full of regrets for abandoning his humanity.

Ultimately, Kokushibo is defeated, but not before nearly killing all of his opponents.

Kokushibo vs Yoriichi: The Brotherly Duel

The saddest part of Kokushibo’s story is his broken bond with Yoriichi. Even after turning into a demon and meeting him again years later, Yoriichi, who is already old and blind, almost defeats him with a single strike.

The encounter shows the wide chasm in their abilities and highlights how even after gaining immense demonic powers, Kokushibo was no match for his brother’s natural talent.

The duel ended without Yoriichi dying at Kokushibo’s hands; instead, Yoriichi passed away standing, with no injuries, a poetic testament to his sheer willpower and strength.

Psychological Complexity: Kokushibo’s Inner Conflict

Kokushibo is not just a villain. He’s a deeply conflicted character consumed by envy, shame, and regret.

His story is tragic, highlighting how ambition and jealousy can lead even the most honorable warriors to ruin. He admired Yoriichi and longed to surpass him, but instead became something unrecognizable, even to himself.

In his final moments, Kokushibo weeps, not because of his death, but because he lost sight of what truly mattered: brotherhood, integrity, and self-acceptance.

Why Kokushibo Is One of Demon Slayer’s Best Villains

Kokushibo stands out as one of the most nuanced antagonists in Demon Slayer. His terrifying strength is matched only by the tragedy of his backstory.

He’s more than a demon, he’s a cautionary tale about the perils of envy and the longing to be more than we are. From his tragic origin to his visually stunning battles, Kokushibo leaves an unforgettable mark on the Demon Slayer saga.

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FAQ

What breathing style does Kokushibo use?

Kokushibo uses Moon Breathing, a style he developed as an offshoot of Sun Breathing, which features unpredictable crescent-shaped slashes.

Who was Kokushibo before he became a demon?

Kokushibo was originally Michikatsu Tsugikuni, a samurai and the twin brother of Yoriichi Tsugikuni, the strongest Demon Slayer in history.

Why did Kokushibo become a demon?

Driven by jealousy of his brother’s talent and a fear of death, Michikatsu accepted Muzan’s offer to become a demon in order to gain immortality and greater power.

Who defeats Kokushibo in Demon Slayer?

Kokushibo is ultimately defeated by the combined efforts of Gyomei Himejima, Sanemi Shinazugawa, Muichiro Tokito, and Genya Shinazugawa, though many of them perish or are gravely injured in the process.