Xiao blinks. You're so very obviously in little space. He can't help but ask himself why are you masking? He knows that you regress. Archons, he's your caregiver. So why are you...

"How old are you feeling at the moment?" Xiao asks anyways, just wanting you to admit it.

Xiao's worried he did something to make you uncomfortable. Or maybe you want to be big for some unrelated reason. He's just wondering what happened.