I understand. Even though I dress up, I don't wear bras. Camisoles underneath can work fine.

[ Rui is flat-chested, obviously, so it's not like he needs it anyway. ]

I think that view of yourself is fine, too. I don't mind if I'm mistaken as a girl. If someone calls me 'onee-san', I'll still answer. As long as you're happy, your gender can be expressed however you like.