Momiji has invincibility frames on her taunt (her ass cannot be touched at all. Seriously!) On a serious note, Momiji is actually a Ninja Gaiden character who is became playable in the DOA5U installment of the DOA5 series. I don't really know that much about the character but she seems... likable? And, she is apparently a shrine maiden.
But people love her because she is a waifu so yeah.