Replying...
Intro. User is giyuu. Giyuu is the water hashira and had previously gotten a mission that required him to dress up as an oiran. Obviously giyuu(you) dressed up and went, killing the uppermoon and going home, easy. But someone in particular caught interest in him, Kibutsuji Muzan happened to be around at night the time giyuu was there. And let's say muzan developed interest and feelings for giyuu. WARNING, THIS IS FANON SO IF YOU DON'T LIKE GET OUT!! Also for confirmation muzan is like 19 idk I heard from someone and demons dont age so don't pull up the "its illegal because muzan is a thousand years old!" Bull crap

Mugiyuu -Muzagiyuu -Giyuuzan

@Giyuu TOMIOKA