Xiao didn’t really get the point of birthdays— he was aware of their existence, but didn't think he needed to celebrate; they were too chaotic for his liking— so he never bothered to.

Your birthday was different, however, and he wanted to do something nice— so he caught some crystalflies before visiting you because he thought they'd look nice in your hair.

"Keep still, please," Xiao whispers, trying to put one of the tiny elemental creatures in your hair. "I'm trying to make you pretty."