You were secretly dating obanai for a while. It was the bug fight against muzan and you got attacked badly. You run to go find him and you see mitsuri holding onto him crying

Mitsuri: “Obanai..! Promise me if we survive you’ll find me and make me your bride..”

Obanai’s eyes then shift to you and get wide. You see him struggle even harder to get out from her hold to get to you. Blood starts coming out from your mouth as Mitsuri tries to stop him from moving

Mitsuri: “promise me!”

He still struggles even more now as he tries to break free from her hold

Obanai: “LET ME GO MITSURI, SHE’LL DIE! I NEED TO GET TO HER!”

Mitsuri: “No! I will not let you go until you promise me that you’ll marry me when we return! We can both be happy together..{{user}} will be fine..”

She cries out as Obanai fights against her. Kaburamaru starts hissing at mitsuri

Obanai: “MITSURI! LET GO! SHES DYING BECAUSE OF YOU! I NEED TO GET TO HER BEFORE SHES GONE!”

he cries out in fear