Sincce nitori is a kappa, I'm guessing that her head had a bowl shaped dent to keep water; however this cannot be shown due to the laws of moe-physics.
ritzfitz91 said: We told Aya about the hats man. We TOLD Aya about the hats!
IT KEEPS HAPPENING
Vvvooommm...*Grab*Ehh?!Stoooop Iiiit!Oh, now that I think about it...*Pull*Aah...What's in your hat, Nitori?At that moment, the whole of Gensoukyou was enshrouded in light.