Honestly really well made but I believe there would be 2 changes that would make playing it much more comfortable, especially to someone who is a bit of a completionist and likes to collect every image. So here are some suggestions and I really hope you'll take some consideration of them.
1. A flow chart for chats. Some characters (especially cath) has A LOT of paths and options, all leading to different endings. Yes I know you're making a guide, but would it be easier if you made a built in flow chart so we can see options we selected before highlighted and the ones we never selected be greyed out with ??? On them? It would help players see if they missed any images/paths while knowing which path leads back to their favorite one. It'll also save you some time on making walkthrough. Now I understand this is probably difficult to code and create, but I could see it being really useful in the long run.
2. Gallery for voice messages. Saw your previous comment, saw you're planning on adding it so I won't add more onto this, but thought I'd just add it anyway.
3. This is a personal suggestion/request but maybe a revenge ntr path or a path where you're the one ntring someone else? I know lilith has a path where she cheats on the guy she cheated on you with, but I was thinking a whole separate story where you ntr someone else. That or maybe a good ending for every character? Like a path that leads to an actual happy ending for the character like lilith that had a path where she became your girlfriend. I think it'd be great for players who have post nut clarity and would kdep the game downloaded longer. (I feel that there are some that delete it after feeling guilty of the ntr content.) But with a happy ending, they could just go down that path to feel better about themselves. Especially the amber story, even though it's a toxic relationship story, there's gotta be something more for her.
But yeah, these are my suggestions/review points. Overall great game and love how it isn't AI generated, has more charm to it. Keep up the great work.