Who is upper moon 1

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Last updated: April 17, 2026

Quick Answer: Upper Moon 1 in the 'Demon Slayer: Kimetsu no Yaiba' series is Kokushibo, a powerful demon with a moon mark of one on his forehead, and the first of the Twelve Kizuki. He wields a Nichirin Blade and possesses the Demon Blood Arts of the Moon Breathing style, which he created.

Key Facts

Kokushibo is the strongest of the Twelve Kizuki, holding the Upper Moon 1 position since the 17th century.
He was originally Yoriichi Tsugikuni's twin brother, born in the 16th century.
Kokushibo awakened his Concentration: Constant ability, allowing continuous demon power usage.
He achieved 67% Total Concentration Breathing mastery, far above other demons.
His death occurred in 1912 during the Infinity Fortress arc after battling Tanjiro and others.

Overview

Upper Moon 1 is the highest-ranking member of the Twelve Kizuki, the elite demon hierarchy serving under Muzan Kibutsuji in the 'Demon Slayer: Kimetsu no Yaiba' universe. This title is held by Kokushibo, a centuries-old demon whose immense power and strategic mind make him the most formidable foe among the Upper Moons.

Kokushibo was once a human swordsman named Yūichirō, the older twin brother of Yoriichi Tsugikuni, the creator of Sun Breathing. After failing to achieve his brother's legendary status and succumbing to jealousy, he accepted Muzan's blood, becoming a demon to attain eternal strength and surpass his sibling's legacy.

Full Name: Kokushibo, formerly Yūichirō Tsugikuni, was born in the 1530s during Japan's Sengoku period.
Rank: As Upper Moon 1, he led the Twelve Kizuki and reported directly to Muzan Kibutsuji.
Abilities: He mastered Moon Breathing, a derivative of Sun Breathing, creating ten distinct forms.
Physical Traits: Kokushibo has three eyes, with a third eye opening on his forehead when using full power.
Lifespan: He lived for over 400 years, making him one of the oldest and most experienced demons in existence.

How It Works

Understanding the role and mechanics of Upper Moon 1 requires examining his powers, rank structure, and narrative significance within the Demon Slayer Corps' world.

Concentration: Constant: This rare ability allows Kokushibo to maintain Total Concentration Breathing indefinitely, unlike humans who tire quickly.
Moon Breathing: He developed 10 distinct forms of Moon Breathing, each mimicking crescent-shaped slashes and enhanced by demonic speed.
Demon Physiology: His body regenerates rapidly, and he can manipulate his blood demon arts to extend his blade mid-swing.
Combat Endurance: Kokushibo fought multiple Hashira-level opponents simultaneously and remained standing for hours.
Third Eye: When activated, the eye grants precognition and access to deeper demonic knowledge, tied to his emotional trauma.
Weakness: Despite his strength, he is vulnerable to Wisteria flowers and decapitation by a Nichirin Blade, like all demons.

Comparison at a Glance

Here’s how Upper Moon 1 compares to other key figures in the Demon Slayer hierarchy:

Demon/Human	Moon Mark	Strength Level	Notable Ability	Defeated By
Kokushibo (Upper Moon 1)	1	99	Moon Breathing, Third Eye	Tanjiro, Giyu, Muichiro
Dono (Upper Moon 2)	2	85	Love Breathing, Emotional Manipulation	Giyu Tomioka
Muzan Kibutsuji	—	100	Shapeshifting, Blood Manipulation	Multiple Demon Slayers
Yoriichi Tsugikuni	—	98	Original Sun Breathing	Died naturally
Tanjiro Kamado	—	90	Adaptive Breathing Styles	Still active

The table highlights Kokushibo's dominance over other Upper Moons and most Hashira. While Muzan remains the apex, Kokushibo's combat prowess and breathing technique mastery place him just below. His defeat required a coordinated effort from three elite fighters, underscoring his status as the most dangerous demon next to Muzan.

Why It Matters

Kokushibo's role as Upper Moon 1 is crucial to the series' exploration of power, legacy, and emotional trauma. His backstory adds depth to the conflict between humans and demons, showing how personal failure and envy can lead to monstrous transformation.

Narrative Depth: His connection to Yoriichi enriches the lore, linking the past and present storylines.
Combat Benchmark: Fighters who survive encounters with him, like Muichiro, gain immense recognition.
Thematic Symbolism: His third eye represents unresolved regret and the burden of living in another's shadow.
Power Standard: His defeat marks a turning point, proving that even 400-year-old demons can be overcome.
Inspiration for Others: His mastery of breathing styles influences later characters' training and development.
Legacy: Even after death, his techniques live on through copied forms used by other demons.

Ultimately, Upper Moon 1 is not just a title but a symbol of the tragic cost of seeking power at any price. Kokushibo’s story reminds readers that strength without purpose leads only to isolation and destruction.