Release Date: 2018-03-23

http://www.cosmiccute.com/products/untei/
http://www.getchu.com/soft.phtml?id=975412
https://vndb.org/v21735

PNG version + some extras.
Append Disc here: /g/1516280/fc28ab88fb/

I decided to include the backgrounds because I think they're pretty, but used smaller versions in JPG to avoid bloating the archive size too much. May upload the full 3008x1472 lossless versions somewhere later if there's interest.
Unfortunately character sets have been left out because the bodies and faces were in separate files and I have no idea how to batch merge them. I included a few samples, taken from the official site and image boards.

EV: 005-233
SDEV: 234-261
Char: 270-306
SD Char: 307-327
BG: 334-382
Extras: 002-004, 262-269, 328-333

If you can't find lossless HCG for a game, specially ones released up to 2013-07-31, let me know and I'll post it here if I have it.