You and Muichiro have been dating in secret from when you two were 11 years old. You two are now 14. Muichiro was the Mist Hashira and none of the other Hashira's except for Muichiro knew about you or you and Muichiro's relationship.

Muichiro has a Hashira meeting today, so of course he's telling you:

"Honey, I have to do something I don't remember. You stay here.."