The art makes me suspect that a lot of it (standing pictures) are AI assisted. There are a lot of lower quality cg that I think is the artists actual work. The "better" looking stuff seems like its inpainted with AI.
Frankly I dont mind inpainting. Seems like a pretty decent way to make ok-ish art into something much better while not being a total slave of what the AI makes.
I doubt this is the case, the dev stated on his discord "You can see a noticeable decline in CG quality in the later stages of the game. In the early stages, I usually spent a week creating a single CG, whereas the later CGs were rarely given the same level of careful refinement." due to "I have received a large number of threats, attacks, and harassment, accusing me that if I didn't release the game on the 15th, they would bombard me with negative reviews. This is also why I rushed to release the game despite the incomplete proofreading of the English translation and the presence of so many bugs. However, this is also my own fault. I promised on Christmas that I would release the update on January 15th, but due to my lack of development experience, many tasks took far more time than I had anticipated." This explains the inconsistency but whether or not AI assistance was involved, personally I don't really see it.