I'm unimpressed by yet another demeaning balloon-boobs image of Yoko Ritona / Yomako-sensei. Such images are a dime per dozen and reveal artists' anatomical lack of knowledge.
It's a fantasy, not an anatomical diagram. Why don't you go around bitching about how all anime characters have eyes that are about 8 times to big, tiny folds of skin instead of noses, tiny mouths with no lips, heads way too big for their body, hair that doesn't come in hundreds of strands but rather a few clumps of plasticine-like material...