Yep. Fate Hollow Ataraxia, you can DL it in Japanese
here. You got to mount the image via Demon Tools, then just copy all the data directly to your hard drive, don't try to install it, because installing doesn't work. However, you can just use the FateFD.exe in the game directory and it will work fine.
You then need to get the English translation patch
here. Supposedly it is only 99% ready, but there were absolutely no problems with me and I got a 100% completion rate when I finally finished the game yesterday. And I mean "finally" because the game has a very long playtime, about 25+ hours in real-time.
It's really worth it if you know the characters and wanted to see more of them. The plot is really good, too, as is the music (for a visual novel). If you haven't played Fate/Stay Night, you probably would want to do that first, because otherwise you won't be able to really get the story and characters. You can download that game in English for free
here. Please remember that that game has three distinctly different routes, which change the story considerably between them (and the behaviour of the main protagonist, who is quite annoying in the first route and becomes a total badass in the second one), so it really is worth it playing through the first game multiple times.
Small warning, both games are eroges, so there are a few sex scenes in them (four in total in Fate, IIRC, about five or six in Ataraxia). But they are quite tastefully done, aside from the very last one in Ataraxia, but that is actually plot related and not gratuitous.
Not that I expect you to put down DA:I until you've finished it.
Damn, mine is still downloading, although it went on all the night. And now I got to leave for work again and basically won't be able to play at all until Saturday. Oh, well. At least there I'll get in a good chunk of uninterrupted playtime.