I found out when a Transfur user posted about it in Twitter and strange enough, it seems like you can take a look at all 3 volumes for free. Unless I'm wrong and they're trying to ask me for money somewhere that I don't really see because it's in Japanese and it isn't showing up in a Pop-Up.
Anyway the transformations of these girls are drawn in some amazing TF sequences with a strange trigger where they change if they get into contact with blood. The first volume is about our protagonist:
https://www.mangaz.com/book/fin/71861
The second volume introduces a new girl who's an idol who also has the ability to turn into a rat:
https://www.mangaz.com/book/detail/71862
(Has a great TF sequence on page 38-39)
The third volume is the finale where a 3rd transforming rat girl is introduced and is an assassin and works with the antagonists that pursue the heroes:
https://www.mangaz.com/book/detail/71863