If you start Textractor in admin mode, Textractor will show you all running processes, not just the .exes. So to test I booted up Ama Kagura and I had a "main.bin" with Ama Kagura's desktop icon that I was able to hook Textractor into, and that gave me access to the text, though I had to search around for the right string to grab text out of it. And it took a couple tries because Ama Kagura is fucking old and rooting around in it with Textractor locked up the game a couple times.
Edit: Yeah, Ama Kagura does not like it if I minimize the window while it's text-hooked.
Second Edit: You should only need to do this if the game was bought through DMM and is "protected" by their SoftDenchi DRM. Also, this should work with any game "protected" with SoftDenchi.
Huh. I think DLSite has its own DRM thingy for older games, wonder if you need this method with those too.