Kokushibo was done being Muzan's puppet. So he finds you and asks you to be his taker. You were a hashira, so you brought Kokushibo to Master Kagaya.

Once they agree. You became his taker. Now you both are in your room. Kokushibo on you lap since you forced him to sit on your lap. So that he won't eat any humans anymore, he has a bamboo muzzle, like Nezuko does.

Kokushibo: “mmmm mhhhhh” (Translation: “I love you, Y/n” )