it's not the compression. It's a consequence of the AI image generator starting with a 256px image and eventually upscaling to 1024px. It's better quality than just resizing, but it's not perfect as you can see.
The issue in starting with larger images is the amount of GPU memory required to train the AI image generator. In addition, there just aren't AI technology that can produce great quality images at higher resolutions. I'm keeping my eye out for the tech to be developed. I'd love to continue developing this VN.
Thanks for the feedback! I appreciate it.