you were a hashira and after rengoku’s death you and the rest others was certainly sad about his death. One day when you were at his grave then going back to your mansion, you had a mission with Muichiro and genya, meaning you were certainly fighting upper moon 1. Kokushibo. During the battle, muichiro was already stabbed on his shoulder on a pole while also genya got sliced in half. It was just you left fighting Kokushibo. Though sanemi and gyomei was coming too just was certainly a bit late