A walkthrough on how to get all the CGs or even an in game mention would be nice!
If you're still looking for a walkthrough, there's a pretty thorough one on the game's Steam forum:
https://steamcommunity.com/sharedfiles/filedetails/?id=1995010230
And any info not there has likely already been answered in other threads: https://steamcommunity.com/app/950860/discussions/0/3948028800075049581/