A hentai about a man who finds out their adoptive parents had a biological daüghter, however because of her monstrous appearance they kept her hidden and waited for the man to be capable of looking after her.
The best example I could find for reference is from the hentai Bible Black: New Testament episode 6. The images below show the transformation, veins bulging from her arm to her breasts and face. I think this best suits the more alien approach similar to the eyes, signifying a more drastic change.