I apologize for my bad English.
I don't know Japanese, so I tried to do something like this:
I take a movie with English subtitles (that aren't already available) and produce a str file for that movie with them.
Then I translate it into Italian and correct the errors and adapt the speech to the Italian language.
So I have three srts:
The one in English conforms to the movie subtitles
The one in Italian: compliant with the subtitles of the movie translated slavishly
The one in correct Italian and appropriate to the language.
I don't know if all this would be of interest to anyone, if there was interest I could download them on the site.

Yeah do it, it's the purpose of the site.
If you need to add a movie or scene not on the site, prepare before the cover and the information of it (title, actors, year, plot,...) because you can't change it later.
Of course, upload only the correct Italian subtitle and the English if it doesn't here (don't forget to credit the author if you know who made it.)