I don't have it, but search for the author who made the angelization series. You'll find it. I think it's being sold separately as well.
If you're still around, rename/copy paste Letter_24 (should be in the same place) to Letter_437. I remember doing this myself, but it's because the game apparently looks for 437 and the one it needs is 24. A lot of people ran into this problem.
In summary: He's still working on it and it might be very slow progress but he's doing it.
This is also a message for anyone interested too. The dev updates primarily on their dlsite creator page. (All in Japanese, though.) They do have a twitter and pixiv, too, but the dev normally seems to talk about himself and development through their given dlsite blog.
Back near April he posted the below on his blog page. You can skip a paragraph if you don't want to know about his personal matters. I threw it all into a machine translator and did very minor edits, but the meaning should get across okay. The second spoiler post is a more recent update to his current development status.
The second post below is from last month. [Comments in brackets like this are made by me.]
He also likes a character called Yumiko since the last few posts highlight her here and there. There's even a doujinshi made/pushed by the dev themselves on their dlsite page. (Yumiko's an older teacher lady who creeps on Seijiro.) There's a LOT of fan art / dev art of her floating around. Relevant because the dev might throw her / might have already thrown her into the game. I don't think she was in the first game, and I don't remember if she was in the current GakuDon demo, either.
