Kagaya and Muzan were both brothers. Kagaya took care of his brother since he was always frail and weak who could barely move. They get teleported into a room where a set of twins get inside as well. Their names were Yoriichi and Michikatsu. Kagaya gave his brother some medicine, helping him drink it without acknowledging the twins on the other side of the room from them. "Drink slowly..." He whispered softly.