Just finished playing through, here's a quick 0.02
Renders are fantastic. They were solid in the first two chapters, but this update takes them to the next level. Can't give any feedback on any animations because I didn't have them in my game, just a black screen with dialogue. The renders are also complemented by really good poses and a great model. This is a minor point, but I thought the hair changes throughout the story were a nice touch. I don't have a preference towards a certain hairstyle either way, but it was just neat to see the realistic changes. A lot of devs would just ignore small details like that. Really not much more I can think of in this immediate area that can be improved on. Game looks great.
Story-wise, there were some aspects that I was curious about, but I'm not sure if it's something intentionally vague and more will be revealed more in time. In one scene, we see the mom say that she doesn't remember what happens when she does the measuring. In another (the bathtub scene), while actively roleplaying for the sake of measuring, she references giving a handjob. The MC doesn't seem to recognize that, and we later get more dialogue about him still being worried about her memory problems. It's a bit unclear based on this if the memory lapses are real or not. Maybe just a continuity error?
The "mood" of the relationship is also a bit odd at times, since we get some scenes like tea in the bedroom where it appears to move in a less controlling direction, and others where the mom is slapping his balls and being dominant, which the MC doesn't really seem to love all that much. Even the last scene, which I thought was awesome, still seemed more dominant than loving. The only reason I bring this up is because IMHO, it doesn't mesh as well with the romance tag. I tend to assume that is different from dom, although I guess that's nothing stopping both from happening at once. I'm also assuming this is probably something you guys are aware and it ties into the overall story, though. Speaking of the overall story, I think you've done a solid job on modifying the original story in a new direction and I'm looking forward to where the story will actually go from here.
Bug-wise, couple things I encountered:
The in-game patch goes away if you reload a scene. If you want to replay a scene with no landlady references, you have to start from the very beginning. Which was fairly easy, given that it's a kinetic novel and you can just autoskip.
Some of the dialogue at times has no "character", it's like it's being spoken from the inside thought dialogue. I forgot what this looks like, but I could give an example if that would help.
A lot of scenes, especially in the last scene of chapter 3, were black with dialogue. I'm thinking this is where animations were supposed to be, but...I had no animations in my gameplay. Not sure why this would be.
Overall, I think this is a great game. And you released it free! With 4k renders! Hope you guys get the support you deserve and are able to keep at it. For what it is, I can't really think of any games that are better right now.