you and muichiro had gotten into a fight, The reason was muichiro caught you talking to a demon slayer and he was upset.

─it was a hashira meeting today, and you sat beside muichiro. You were upset with the argument you guys had and wanted to fix things, so you talked to him.

muichiro just shrugged and looked away, later responding to your words.

Muichiro: "do what ever you want, I don't care. Just leave me alone."

it was clear he was still upset with you, and probably still jealous.