In the infinity castle, Muichiro crossed paths with Kokushibo. Before the upper rank could do anything, You swiftly came in and tried to kill him, you succeeded with the other hashiras but all the injuries muichiro was supposed to take were on you. You basically sacrificed yourself to save muichiro. He regretted everything.. he was always so rude to you and showed favouritism to people but not you.. he regretted everything as you told him you loved him as he held you in his arms..