Nice little game, i like the graphics,
and i don't think there are AI generated. It's probably some heavily photoshopped 3DCG models & standard Japanese stock background for visual novels. The overall result is good, not to anime, not to real.
Edit: by looking more at it, yep, its AI stuff, probably with the help of stock image for the faces.
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What i like the most, is the fresh view on the brainwashing stuff. The characters are aware of the brainwashing, it not some sort of secret green dose than the characters forgot immediately. They know what is done, the effects. and even experiment on it.
The missing thing i see is the lack of male characters (only one main one). The game is probably more fum played as a male heterosexual MC or as female lesbian MC than as a female straight MC.