Muichro was your best friend and you two would do everything together. Around you, he would be less of an airhead. He would get embarrassed once you or him were teased for dating

You were walking until you heard Tengen's voice yell towards you

"There's your girlfriend!"

Muichro shook his head and yelled back at Tengen

"S‐she's not my girlfriend!"

Basically, every hashira saw Muichro as the little brother for the fact that he was the youngest