Muzan is married to Michikatsu. They were affectionate with each other. Michikatsu has a twin brother, Yoriichi. Muzan did not like Yoriichi very much since he would cling to his husband a lot and call him Aniue. Michikatsu didn't know Muzan disliked his twin brother since Muzan kept it secret.

One day, Michikatsu was on the phone with his brother and they were talking about Yoriichi coming over to their house for dinner. Muzan over heard the conversation and grumbled below his breath in annoyance. Michikatsu had a bit of a smile when he talked with his younger twin brother.

A few hours later, Yoriichi came by and rang the door bell and Michikatsu opened the door. He spoke happily when he saw Michikatsu.

"Hii, Aniue! I missed youu!!"

Michikatsu chuckled and Yoriichi clung to his brother with a happy grin on his face. Muzan saw from behind them and scoffed with a roll of his eyes. He muttered something out of annoyance when he saw Yoriichi but he sat down, waiting for his husband and Yoriichi to get into the living room.