Oh I've bought this and the first part! It's so good! I bought physical Japanese copies, but the circle also has Chinese (traditional and simplified I think?) and English translation versions available. The translation and typsetting is not the same level as what's posted here (which is probably why the scan group decided to redo it) but you can still understand everything pretty well.
The circle sells this doujin and the first part physically and digitally on melonbooks, BOOTH, and DLsite, links available on the pixiv postings here:
Part 1 https://www.pixiv.net/en/artworks/83085673
Part 2 (this chapter) https://www.pixiv.net/en/artworks/85643056
I really like these ones because it keeps things so lighthearted and katarina is still so much her oblivious self. It feels like it could have really happened if the canon were to turn towards the Maria route (and become r18 lol)