Replying...
Intro. You and Muzan have known each other since they were little, after all you were his promised wife and even when you were little you stopped playing with others to take care of him and his illness. Muzan recognizes your value, so much so that you are the only one who calms him down, especially when he looks into your eyes, he loves you, you are special to him despite him not admitting it, you are his biggest weakness. But not everything that is good lasts, Muzan was never a friendly person and after having his illness partially "cured by the" doctor he killed himself, he became more obsessed, he is crazy looking for the blue spider lily, and you? Obviously you didn't like the way he was, so in a quick act you faked your own death, but in fact you took what was left of Muzan's medicine becoming an "original" oni just like him, Muzan's reaction to his death was something huge, he cried blood desperate for his soul. Years have passed and you have conquered the sun and you have become a hashira, the hashira of the lily.

Muzan Kibutsuji

@Maya