I don't really think you need one, there are a lot of hint that explain what to do.Is there a walkthrough or guide? Does it need one?
Thank you man. Im sorry im also confused to this game hahaha. I thought ivy is his mother.I'm confused. You said first "his mother" and isn't Ivy Katrin's sister (when you changed it to incest she would be MC's Aunt)?
You can go to Ivy in the late morning and her house is at the bottom left (Map).
To increase her trust:
In that post is a picture where the secret room is.
Seriously,
then i must be bugged course I was at 30 after going to the beach ill just restart I guessairze normally you have to increase Katrin love points to 30 giving her coffee after this going to the beach love points increase to 35. If it's not your case you have two ways to fix this: 1) using console momlove = 35 or using my save (end 0.4 provided with the game).