The 4th DLC for Oboromuramasa has been announced today and it features a small demon girl as a playable character that can change into differend forms.
She has her default child form, her more grown up teenage form and her huge muscled demon form.
It seems that all 3 forms are playable even though she only floats around in her demon form, but its better than nothing.
So far it has only been announced for japan, but the other DLCs have already been released in the west so it's only a matter of time untill we get it.
You can watch all her transformations
here but i highly recommend to watch the whole video since it has some very nice music.