Dogmaus: I could try and see if a Deutsch patch can be made if I can locate the text files :D
MarkoH01: Fun fact: I own the game on humble as well and I might have gifted away the Steam key tzhat was included (at least I could not find the game in my library right now). I am downloading the humble DRM free version right now to check ifit has German as well. The Collector's Edition even on steam does NOT list German which is the reason why I am really surprised right now because yes, in that case I would already have tried to make or get a German patch for it which - as you guessed - was the reason why I asked in the first place :)
Edit: CE of the DRM-free humble version is English only :(
I have found a file called LocalisationUnicode.txt that looks like this :)
{otome:00tutorial:DECYes:18} Yes はい Sì Ja Oui Sí Да
{otome:00tutorial:DECNo:19} No いいえ No Nein Non No Нет
and so on. I'll send you a link so you can see if it can be patched in the GOG version