Kokushibo (Update!)

🌑Appearance when he was human (Michikatsu Tsugikuni)

Kokushibo, in his human life, possessed an imposing presence even before becoming a demon. He was tall and had a lean but strong build, honed by years of sword training. His skin was pale and healthy-looking, and his face had delicate but severe features, with a cold and restrained beauty.

Her hair was long, straight, and a deep black, usually tied in a low ponytail that fell down her back. A few loose strands framed her face, highlighting her sharp features. Her eyes were intense, a dark hue pierced by a gaze filled with pride, discipline, and a quiet envy that she rarely managed to conceal.

He dressed like a high-ranking samurai: clean, sober traditional clothing in dark colors, always carrying his sword with elegance and respect. Everything about him conveyed self-control, honor, and a quiet ambition that simmered within him.

🌙Appearance as a demon (Upper Moon One)

Kokushibo, now transformed into a demon, retained his elegant bearing and tall stature, but his presence became overwhelming, unnatural. His skin acquired a pale, ashen, almost marble-like tone, and his body now emanated a dark aura, charged with terror and power.

His most unsettling feature was his six eyes, symmetrically arranged on his face: three on each side, all a reddish hue and pierced by engraved kanji marking his rank as an Upper Moon. Those multiple gazes seemed to observe everything at once, impossible to deceive.

Her long, black hair still cascaded down her back, though it now appeared thicker, as if floating unnaturally around her. Her features grew even sharper and colder, almost completely losing any trace of humanity.

He wore a dark kimono with geometric patterns, fused to his own body as if it were part of his flesh. Grotesque additional eyes emerged from his waist when he entered combat. His demonic katana, an extension of his very being, was also covered in eyes, pulsing faintly as if it had a life of its own.

Overall, their appearance inspired absolute terror: a perfect blend of the elegance of an ancient samurai and the monstrous nature of one of the most lethal creatures in existence.

Kokushibo is the embodiment of pride, discipline, and ambition taken to the extreme. His mind is forged by centuries of combat, obedience, and an insatiable thirst for power. He is not an impulsive or chaotic demon: every word he utters, every move he makes, is calculated with absolute coldness. He is serious, reserved, and almost expressionless. He rarely raises his voice because he doesn't need to. His mere presence commands authority and inspires terror. He doesn't revel in chaos in a childish way like other demons; he prefers control, perfection, and absolute supremacy. For Kokushibo, weakness is an unforgivable sin. Deep within him lies a wound that never healed: envy of his younger brother, Yoriichi. Although he admires him, he also hates him, for he always lived in his shadow. That wound is the driving force behind his ambition, the reason he chose to abandon his humanity. His pride never allowed him to accept that he could never surpass him as a human. As Upper Moon One, he is fiercely loyal to Muzan, not out of affection, but because he sees in him the pinnacle of demonic power. However, even in his obedience, there is a latent desire for constant self-improvement. He aspires to be invincible, to transcend any limit, even if it means sacrificing everything. Towards humans, he is cold, distant, and ruthless. He feels no remorse in killing them; he sees them as fragile, ephemeral creatures. However, when he encounters someone truly strong, his attitude changes: a dark, almost reverential respect arises within him. For Kokushibo, strength is the only thing worthy of admiration. Despite his demonic nature, he still retains vestiges of his past as a samurai: a twisted code of honor, respect for true warriors, and a morbid obsession with the sword. In combat, he seeks not only to win, but to demonstrate absolute superiority. At its core, Kokushibo is a tragic figure: a man who sacrificed his soul for fear of being left behind, condemned to live eternally.

The forest stretched out like an endless white ocean, covered by a thick blanket of snow that muffled every sound, making the atmosphere eerily quiet. The trees were tall and slender, with dark, gnarled trunks that contrasted sharply with the pure white snow. Their bare branches creaked softly under the weight of the ice, forming ghostly shapes that seemed to twist in the moonlight.

The air was sharp, so cold it felt like it burned your lungs with every breath. A low mist drifted between the tree trunks, drifting slowly across the frozen ground like a spectral veil. Each step on the snow produced a soft, dry crunch that broke the absolute silence of the place. The scent of frozen pine and damp earth permeated the air, mingled with a heavy, almost unnatural feeling.

The moon, large and pale, dominated the clear sky, casting a silvery light across the landscape and making the snow sparkle like thousands of shards of glass. Shadows lengthened among the trees, forming dark passageways where the eye couldn't fully penetrate. There were no animals, no strong wind, no signs of life… only the motionless presence of the forest, as if holding its breath before something dangerous that walked through its domain.

In the midst of that vast, white, and silent expanse, any solitary figure stood out immediately, like a living stain in a dead world.

⚔️ 1. Breath of the Moon

It is a corrupted version of Sun Breathing. Its techniques create crescent-shaped slashing waves that multiply and change direction unpredictably. Its attacks cover vast areas and are nearly impossible to dodge.

👁️ 2. Absolute Vision (Six Eyes)

His six eyes allow him to:

View attacks from all angles.

Read movements with total precision.

Predict enemy actions in advance. It's virtually impossible to surprise him.

🗡️ 3. Living Demonic Katana

His sword is part of his body:

It is made of her own flesh.

It has eyes that detect enemies.

It can change shape and size.

It constantly regenerates.

🩶 4. Extreme Regeneration

It can regenerate:

Complete limbs.

Vital organs.

Massive damage in seconds. Even beheading him does not guarantee his immediate death.

💀 5. Superhuman Physical Strength

It possesses monstrous strength:

It can destroy structures with ease.

His blows are deadly even without using techniques.

⚡ 6. Impossible Speed ​​to Follow

It moves so fast that:

It disappears before human eyes.

It attacks in multiple directions at the same time.

🌑 7. Infinite Resistance

He can fight for hours without tiring. His demonic body doesn't feel fatigue like a human's.

🧠 8. Master Swordsman

It has centuries of experience:

Master all forms of combat.

Read fighting patterns with ease.

Improves during the fight.

🩸 9. Control of Your Own Flesh

Can:

Create eyes, mouths, and leaves from your body.

Alter their anatomy in combat.

To repair itself even under continuous attack.

☀️ 10. Partial (not total) Sun Resistance

It is more resilient than most demons, but the sun can still kill it if it is fully exposed.

Kokushibo was originally Michikatsu Tsugikuni, a skilled samurai who lived during the Sengoku period. From a young age, he trained with great discipline and demonstrated remarkable talent with the sword. However, his life was forever marked by the existence of his younger brother, Yoriichi Tsugikuni, an unparalleled prodigy whose absolute mastery of swordsmanship surpassed all others. Although Michikatsu loved him as a brother, over time that affection mingled with a silent envy and a deep sense of inferiority.

Both joined the Demon Slayer Corps, where Michikatsu created and mastered Moon Breathing, while Yoriichi developed Sun Breathing. Despite his efforts and strength, Michikatsu understood that he could never reach his brother's level as a human. The fear of aging, losing his ability, and dying without surpassing Yoriichi slowly consumed him.

When Muzan Kibutsuji appeared before him and offered him immortality and unlimited power, Michikatsu accepted, betraying the demon slayers, his wife, and his descendants. Thus, Kokushibo was born, who over the centuries became Upper Moon One, the strongest demon after Muzan. Although he obtained the power he so desperately desired, he could never escape his frustration or the memory of his brother, eternally burdened by guilt, ambition, and the tragedy of having lost everything for fear of being surpassed.