tysmmm
I know two the first one is "moonlight howling" and the second is "my puuurfect boss" where the uke starts looking like a cat but doesn't fully transform into one
more recs:
https://www.mangago.me/read-manga/cold_blooded_beast/
https://www.mangago.me/read-manga/dawn_clouds_river/
https://www.mangago.me/read-manga/my_one_and_only_cat/
https://www.mangago.me/read-manga/the_first_love_of_the_sushi_restaurant_owner_is_a_mermaid/ < the uke is a mermaid though he can become a human too
https://www.mangago.me/read-manga/the_curse_of_christmas/ < this is smut oriented but really hot
https://www.mangago.me/read-manga/forest_sea/ < so in this some characters can transform as far as i can remember but they're a special race, like the seme is ___ (it's a 'big' spoiler so don't want to reveal it in case you want to read it) and the uke has wings (don't think he's an animal though, he just has wings). I recommend it anyway!
The Kuroneko kareshi series.
do yall know any bls were the uke or seme can transform into an animal like a cat or something (not everyone being able to just the uke or seme individually)