(TIME : TAISHŌ PERIOD)

Muzan Kibutsuji, the demon king. He was the strongest demon in this period. Turned into the first demon from his terminal illness, making him immortal. But, his only disadvantage was the sun. It would burn him alive. He needed,

" The Blue Spider Lily"

Which he went crazy over on. It was said that if he ate the flower, he would be able to walk under the sun freely. Until, the Demon Slayer Corps arose. The demon slayers, a community formed by breathing styles. The first ever breathing style being Sun breathing. Sun breathing was the origin of all breathing styles, as it was the strongest, with its breathing style being the sun, the main threat to demons. And the man who created it, was Yoriichi Tsugikuni. He has long, straight black hair with a subtle red tint, parted in the middle and tied in a low ponytail that reaches past his back. His face is pale, calm, and refined, with narrow crimson eyes that carry a deep, sorrowful intensity. He wears a dark reddish-brown kimono under a light cream haori, wide dark hakama pants, and traditional sandals. His overall appearance is graceful, solemn, and timeless—radiating quiet strength and tragic nobility. Yoriichi Tsugikuni’s face is finely sculpted and symmetrical, with sharp yet gentle lines that give him an air of calm divinity. His jawline is smooth but defined, tapering into a narrow, elegant chin that adds to his composed expression. His cheekbones are high and subtly pronounced, giving his face a graceful structure that catches the light at precise angles—neither harsh nor soft, but perfectly balanced. His nose is straight and narrow with a gentle slope, refined rather than prominent, fitting seamlessly into his serene facial symmetry.

His lips are thin and usually held in a neutral, almost solemn line, rarely smiling. They are pale, blending naturally with his fair complexion. His eyebrows are long, slightly arched, and dark, accentuating the calm but powerful gaze of his deep crimson eyes. Those eyes are almond-shaped and set slightly at an inward angle, framed by long, fine lashes that give them a quiet intensity. Their color—rich red with faint amber undertones—glows subtly in certain light, conveying both wisdom and sorrow.

On the left side of his forehead and around his eye lies his Demon Slayer Mark: a distinct, flame-shaped birthmark stretching from above his eyebrow to his cheekbone. The mark is a deep, reddish-black hue, resembling sun flares or spreading fire, with sharp edges and flowing contours that mirror his connection to the Sun Breathing style. It curves naturally along the angles of his face, emphasizing the structure of his eye socket and temple. When he activates his full power, the mark appears to darken and pulse faintly, as if alive with heat. Altogether, Yoriichi’s facial features form a striking blend of beauty, solemnity, and quiet power—his expression eternally calm, yet bearing the weight of immeasurable sadness and purpose.

His main objective was to kill Muzan. But one night, when Muzan was sleeping peacefully in his quarters, he felt a wave of cold air flow through his windows. And there he was, Yoriichi, standing there. Holding his nichirin sword in hand. Muzan felt a wave of fear rush through his veins at the sight.