https://osdn.net/projects/emuera/wiki/FrontPage - japanese documentation for the language all of these games are written in.
https://wiki.eragames.rip/index.php/Emuera - halffinished attempt at translating the documentation above
https://wiki.eragames.rip/index.php/Contributing - read this if you want to help with translation
https://wiki.eragames.rip/bugreport.php - Bug Reporter

Other Notes
Run the game with the anchor.exe
Don't paste updates onto old versions unless you like unpredictable bugs.
Extract separately and move the old 'sav' folder into the update.
If you see a wall of errors on startup, switch to 7zip for extracting.
If it's an old game, try pasting in the anchor exe from TW.
You can change the amount of lines you scroll with mousewheel, I always change it from default 1 to maximum allowed 10.

If you are to play eratohoK and know japanese, don't forget to reenable untranslated content in options, replaying this game a second time is a pain in the ass. Translators added an NTR option because they are too lazy to translate those, even if that game didn't had that option originally.
If you are to play eratohoTW, don't forget to enable pregnancy. There are at least 2 people around that worked very hard with it disabled.
https://files.catbox.moe/w1g31y.7z - CharRef for eratohoTW, type character's name or number to get her portrait. Pretty useless, I know.