I only found this from somewhere else, hope it can help you:

GC345 patch:

“This work was started as an attempt to fix some bugs and script flaws in the original japan MGQ3 and the final Rogue’s MGQ3 patch. The second goal was hieroglyphic spaces removing. The third – Spin-offs Stories fix.

P.S. This full patch mod is backward-compatible with the Rogue’s MGQ3 patch and all “standard” Spin-off stories (developed for the Rogue’s MGQ3 patch).

Unpack the file to the gamedir. The file 0.txt must be in the same dir as mon_que.exe.”

https://www.mediafire.com/file/3qaas7t2e3a3a47/MGQ3_fix_19Apr2014_1622.7z/file

Monster Girl Quest Remastered (720p and 1080p):

“This fan rework of the game comes in two upscaled resolutions: 1440×1080 and 960×720. Please make sure you’ve downloaded the version that best suits your monitor’s resolution.
Also please be aware that the 960×720 resolution has not been tested as thoroughly so there may be some text position/size issues. If you find anything game-breaking, do report it.
Credit to Torotoro Resistance for actually making the game, RogueTranslator for his work (despite the many errors) and GC345 for his fixes to Rogue’s script that allowed us to get side stories working.

In order to use a higher resolution the game now runs using onscripter. The list of improvements is as follows:
1. All the images in the game are fully upscaled to either 1080p or 720p.
2. The need for Save Locations has been eliminated, and saves can now freely be made at any point. Feel free to make saves during a battle as necessary.
3. Some fixes have been made to the original game script, like making sure Tamamo’s clothes don’t suddenly reappear during an H-scene, and generating some scripted damage numbers correctly. Two enemy skills will now check for Fallen Angel Dance to better balance their respective fights.
4. Several missing lines that were generated but not accessed properly have been re-implemented.
5. Many, many typos and grammatical errors in Rogue’s translation have been corrected.
6. The Record has been tweaked and expanded to better reflect the game’s content. Besides making fixes to mismatched counts for enemy skills and endings, there are new entries included that are more specific to them.
7. The Menu and Monsterpedia have been optimized to load faster.
8. A Skip To Line function has been included, which can be accessed from the Extras menu. It was created as a debugging tool, which means it might break your game, but if you know what you’re doing and want to skip to a certain point in the game, simply input the line number in the game script you want to skip to and click the right caret.

While the port to Onscripter expanded what we could do with the game, it also broke many special characters, which had to be replaced. In particular, all the music notes had to be replaced with tildes and rearranged in the script to emulate the expression behind them.
Side stories are compatible with this version of the game, but any custom images in the mod folder must be upscaled manually. Use a program like waifu2x to scale them to 1.8x for 1080p or 1.2x for 720p. Once that’s done, the script will take care of the rest as you play the side story normally.
Any special/japanese characters contained within side stories will also not display correctly.
We worked to find and correct as many bugs and errors in this release as we could, but there is a possibility that some display errors could have been left behind. Please check the download location for the most up to date script patch.
If you have any questions or find any issues to report, feel free to visit us (lugia19 & Sore Eyes) in the NG+ Discord server. An up-to-date invite link to the server can be found on the front page of the Monster Girl Quest NG+ blog at http://ecstasywastaken.blogspot.com/”

Links:
1080p: https://drive.google.com/file/d/1edPlgK7UhBkZs5zGTcxyu9d4ecFtLyBD/view
720p: https://drive.google.com/file/d/1yODyN9mXHcqmm82OPB4L4LqY1ttcFtaI/view
Updates: https://drive.google.com/drive/folders/1lq7JRFPOwtGnBAQAbCp4AsN9c34027UH

Otherwise, I saw many people encounter many problems with this game and they also haven’t found a solution yet ^^