I found this on e-hentai about a shapeshifting couple. I don't know which part is really the part 1 of the comic but the couple is between a shapeshifting fox man and a raccoon or cat girl, I guess she's a raccoon? I can't tell what she's supposed to be. But the transformation sequences in these were pretty good though.
Here's what I think is the first doujinshi about the couple:
https://e-hentai.org/g/1457843/5866b701b7/
The transformation of the woman is here:
https://e-hentai.org/s/5efa31ffc6/1457843-3
https://e-hentai.org/s/e387bb34b6/1457843-4
https://e-hentai.org/s/659c12128b/1457843-5
https://e-hentai.org/s/9f9387d9c6/1457843-6
And here's what I think is the second one about the couple:
https://e-hentai.org/g/1457841/54285c38fd/
Here's her transformation sequence in this comic:
https://e-hentai.org/s/1712f13dff/1457841-27
https://e-hentai.org/s/8a898ea555/1457841-28
https://e-hentai.org/s/9eb0167c26/1457841-29
And that's it. I really should've shared this sooner, especially if what I heard about the site shutting down at the start of next year is true. I just barely remembered this rumor so it may be best to investigate if this is true or not on your own.