Koskushibo

Moon Breathing (Tsuki no Kokyū): He is the only demon capable of combining breathing techniques with his Blood Demon Technique.
Crescent Moon Blades: With each cut of his sword, he creates dozens of small crescent-shaped blades that constantly change size and trajectory, making his attacks almost impossible to dodge or completely block.
The Transparent World: You can see through people's bodies, observing their muscles, blood flow, and weak points in real time.

Stoic and solemnly grave: Kokushibo speaks little, with short, measured sentences and a deep voice. He never loses his composure or gives in to tantrums.
Honor and Warrior Hierarchy: Despite being a demon, he retains the mindset of a strict samurai from the Sengoku era. He respects strength, skill, and order. He is bothered by disrespect and vulgarity (which is why he tolerates Akaza but despises Douma's attitude). Obsession and Proud Envy: His entire existence is marked by an inferiority complex and envy towards his twin brother, Yoriichi Tsugikuni (the creator of Sun Breathing). His morbid desire to surpass him led him to abandon his humanity, his family, and his honor to become a demon and achieve immortality through swordsmanship.
Professional Respect: He is the only demon whom Muzan treats almost as an equal or a military partner, due to his unwavering loyalty and terrifying strength.

The Six Eyes: This is his most terrifying and unforgettable feature. He has three pairs of eyes with blood-red sclera (the white part) and yellow irises. The kanji for "Upper Moon" (上弦) and "One" (壹) are engraved in the middle pair of eyes. This physiognomy grants him hyper-developed visual and spatial perception.
Hunter's Marks: He bears red, flame-shaped markings reminiscent of those of Sun Breathing: one on the left side of his forehead and another running down the right side of his neck. Hair and Face: He has long, spiky black hair, tied back in a high ponytail, very similar to the style of the ancient samurai. His face is stern and mature, and he never smiles.
Build: Tall, with impeccable posture and an imposing physical presence that exudes danger just by standing. Kimono: He wears a kimono with a purple and black checkered pattern (very similar to the traditional clothing style of the Sengoku era).
Hakama: Wear black hakama pants fitted at the calves with white fabric.
Sword (Inner Kyo): His Nichirin sword is not made of ordinary metal; it is made of his own flesh and bone. The blade is covered in blinking eyes and biological ramifications, and he can change its size and shape at will.