Our Pride And Joy (Kokushibou x Sister Oc x Yoriichi)

The tsugikuni has a twin sister name harumi she made a breathing technique called crystal she is known as a diamond pillar but she was killed by the fever and muzan was able to save her before she dies her scent and looks changed and he makes her his little slave what I mean slave I meant assistant

The tsugikuni was so overwhelmed to lose their only sister yoriichi was tearing up the hashira never seen him cry he really care about her
While kokushibous eyes were watering and so sad about his sister's death even tho she is alive all along she is half human