Yeah, nobody really knows anything about him.
We just keep waiting for him to come and say something, or wait for someone with experience to be able to continue with this game for us...
One way or another, the only way is to wait and/or move on.
Honestly, it's best to just
move on and accept what is there from the developer. If he or she adds to the story, we will appreciate it. If this is all the content we'll have, then you already know what I wrote about it. Appreciate all the efforts made and move on.
Non-Canon Christmas Episode Chap. 2
There was someone who quoted me saying
'the Chap. 2 Christmas episode was different, I don't think they're meant to be canon'. Let me show you this screen from that Christmas event which
doesn't appear in the last Christmas event:
That Christmas event specifically states that the story shown is
NOT canon. This statement was never made in Rebecca's story, which leads me to believe that if no future content comes up, Rebecca's story is now the canon after-academy ending.
That said, I do think the dev wanted endings like these for multiple girls - but just didn't get around to it. Note how Rebecca's Christmas story includes far more details interweaving the main story into the Christmas event, which lead me to believe the dev wanted it to be canon (maybe part of multiple possibilities).
For me, as it stands the Rebecca ending is the canon ending. Rebecca isn't my favourite girl by far, but this is what I read from the scenes.