The person's identity is something of a spoiler. I mentioned who it is beneath the spoiler block in
this post.
If you mean where to find her in the basement, then she'll be in this spot for direct confrontation:
View attachment 42613
Or this one if you want to replay the entire cutscene:
View attachment 42614
You have to actually complete the True Ending for either spot to properly unlock, however.
There is only one visual presentation, though her exact appearance during that segment is based on certain choices you can make during the game. It's a true-POV-type thing (in part for plot-related reasons) where you're above her. The encounter does have two phases, though: one which is more like a traditional "battle" in this game (using Resist/Fear/Obey and her having special moves and such), and then once you're about 75% done changes to the "romantic"-style encounter (like the Mnemosyne encounter).
This is just going back from things I recall posted on Ci-en and Twitter, neither of which I am really an expert at or made extra special note of (to be honest I don't use lots of social media), but as far as I know, SQDT is interested in doing more. I have no idea if there is a time frame for any of it or not. The past year I know a lot's done a lot to further polish this game such as putting the game on mobile, doing a physical release at comiket, and working on patching and enabling mod support (and allowing me to work with him on the official English translation...but that is literally the extent of my involvement and so bear in mind everything I say here is as a fan). I know there are further plans to "polish" more, too (obviously, the official English release is still in the works, and there are plans to get it on Steam, too, for example).
The game was originally released in a "1.0" state. This was the basis for the unofficial English patch that I did, as I was pretty intrigued by the game and started work on translating very quickly. While I was in the process of translation, SQDT released various upgrade patches that included things like bugfixes, difficulty balance passes, mod support, and new gameplay mechanics (like an "infinite leveling" system). However, because of the way my process worked, I couldn't go back and add those things to the English translation patch easily, and you can't combine the two (the English patch will overwrite any Japanese upgrade patches you use, and vice-versa). The Japanese version is up to version 1.2. When I was invited to do an official translation, I basically re-translated the entire game again, to work with the upgraded Japanese content. So when the official English release comes out, the plan as far as my involvement goes is that it should more or less be a match in terms of gameplay to the latest Japanese version as well.