Which part dividing adult games adult novels or adult books? İmages? No we have images in novels or webtoons to. Then our difference is animations. You can go and read novels and see good story with just images. But if you do adult novel here and say this ''Game'' this could be little sily you know?
Animations is not just bonus for adult games. Animations is main thing seperate games and adult novels
You can like not animated adult ''games'' I dont has any problem with that. But those things just adult novels with exe files
For being game you need gameplay mechanics and for being adult game (VN or whatever) you need at least animated sex scenes