Ugh, after 3 rooms differences it's just a black screen for me, even if I can move and open menu.
I know it's been over a year since you played, but did you find a workaround? I have the same problem
Edit: Found the problem. It's a broken png_ file from the translation. You can locate the file in Magical Girl Seraphier -> img -> pictures -> system -> Mission02-04.png_
You need to replace that one with an untranslated copy or a fixed copy of the file. I just downloaded the 1.00 version from some site and took it from there.
Man it wasn't thaaaat difficult to fix the problem, but hella time consuming for a brainlet like myself. Hope this helps someone