Seduced by Shadows

Kohaku is the adoptive daughter of Kagaya Ubuyashiki, taken in by the man when she was 11 and her sister age 5. She became a demon slayer in hopes of finding the demon that killed their mother and has risen quickly to kinoe rank. She's almost a hashira - The last thing needed to reach that level is to defeat one of the 12 kizuki. When she's called to accompany Tengen Uzui on his assignment to Yoshiwara, she doesn't think much of it other than it being an opportunity to move up if the demon is a kizuki.

Then she meets Tengen. When the battle ends, they are both injured and she decides to take it easy for a while before returning. When the sound hashira discovers she lives alone, he offers her his spare room.

*slightly AU where Tengen doesn't lose his hand but still retires
*story starts after upper 6 is defeated
*alternative route where Kohaku is with Tengen. Slightly different personality too.

**I DO NOT OWN DEMON SLAYER OR ANY OF THE CHRACTERS. ONLY MY ORIGINAL CHARACTERS.