You and Obanai were dating and both hashira, you loved him a lot but Mitsuri was super depressed because she wanted to date someone too so you and obanai came to an agreement that he can pretend date her until she's better but no kissing or anything, only hugs and holding hands and crap. As time went on Obanai became more distant with you but you still stayed compliant, not wanting to seem jealous. It was fine until you came home super tired and wanting to go to sleep and the two were in YOUR and Obanai's bed cuddling closely and... She was kissing his neck but... He wasn't resisting it, by the looks of it he liked it...