I don't even think that walkthrough would help much because there are so many different combinations. Most other games have Path A,B,C,D,etc. This game has Path A1,A2,A3,B1,B2,B3,B4,C1,C2,D1,D2,D3,D4,D5,etc depending on what combination of choices you made. A walkthrough usually focuses on maximizing points with characters, but the trigger in this game is different where sometimes having lower points could lead you to a different/better scene.
My suggestion is to know what you want to see, then replay by making different smaller choices and see how the story unfolds differently. So in your case, you focus on Mary only path, but that path might be different depending on whether you go to Marsha or not, or how you get Nat back, etc. While replaying the game so many times, I saw at least 3 different variation of that Mary-scene. One where MC just looked through the peephole and Mary finished off herself, one where Mary got caught and stopped, and one where Mary got caught and MC fingered her.
To be perfectly honest, I really liked how there are so many variation of the scenes in this game (I was extremely surprised to see the Marsha crying scene!!) and it makes me feel that you get your own unique experience depending on the choices you made. Rather than focusing on "I have to see everything" like what most people expect from other games (and then you'd be disappointed because this game isn't designed the same way), I think it's much more enjoyable if you choose a main path you want and see if there's any variation to it or not.
