I could totally see Michiru doing something like that though and i could see her scraggly taking Harukas name and milking it for All its worth. Everything is addressed “Mrs and Mrs Tennoh” she answers her own phone when her parents call with “Tennoh residence, other Tennoh speaking” and all kinds of just petty things cause Michiru is many things but being above petty she is not

I AM HERE FOR THIS.

Every event Michiru has to attend her name is always wrong on the list, which her parents intend as a way to not acknowledge the change but ALWAYS just ends up giving her an excuse to smile and say “Actually, it’s Michiru Tennoh now. We should be on the list as Mrs. and Mrs. Tennoh.” It always just draws more attention and puts her parents in the awkward position of everyone knowing they gave the wrong name for their daughter.

And when they have kids it’s SUCH a thing. Michiru’s family absolutely does everything they can to try and change her mind and give them the Kaioh name, because YOU CAN’T JUST CUT OFF YOUR LEGACY MICHIRU. (Though they are perhaps equally relieved and appalled that the kid(s) is/are a Tennoh when at age five they haven’t taken a single music/art/etiquette class and are fingerpainting in kindergarten like some sort of normal lower-class child)