A lot of promise. I'd give this 3.5 stars if I could. A clear 5 if the issues below get fixed.
The Good:
Art/Animation: 5/5. Pretty fantastic production levels for this sort of game. Possibly the best 3d renders I've seen on this site.
Writing other than intro and sexual situations: 5/5 for a VN with adult content. There is a lower bar set for adult VNs of course, and of videogames in general.
The Bad:
Facial expression/text mismatch.
Mainly in the beginning, but throughout some sex parts too. Nothing a few more renders can't fix. I have a feeling this was due to time constraints. But you can't get away with this in a quality game. Expressions must match context.
Intro: Exposition written at the beginning:
Starts awkwardly with a huge chunk of exposition at once. A few choice sentences could give us the gist, with some additional renders to help. Just enough to paint the world and situation for us. Some backstory can also be pushed back further into the game. Suggestion: Rewatch some films or TV shows that do an opening summary well. And I'm not talking about Star Wars.
If you still want to include all of that information right at the start rather than bits and pieces, you're likely going to need a full update worth of renders for it. Plus, the writing will need some work here.
Biggest Gripe: The WAY TOO ABRUPT sexual situation. Plus lack of any stumbling, learning curve, or real hesitance from either character:
(Paraphrasing)
"Say, Pops! Why doncha plop yah cock in muh cheeks?"
"Duh. Well, I dunno, honey."
"Aww c'mon, big daddy. This uterus-train chuggin full-steam-ahead & mom ain't around for your annual dipstick-check. So jiggle these mudflaps, why doncha?"
"Welp. Fair enough." *Shrugs and unzips*
I mean, talk about abrupt and implausible. You *can* throw users into the action right away, but it needs to be done with some choice words and glances beforehand, to paint a picture that both chemistry and understanding were already building off-screen between them long before the start of the game. Maybe in the first scene have her catch MC glancing "again" and tease him about it. And/or vice-versa. Plus a few more choice comments and looks/glances here and there leading up to this point. But you need to show something. It is possible to do abrupt well. But it does take some thought and writing skill to pull off. Foreshadowing is your friend. Additionally, no one's going to be an expert right out of the gate, so the lack of any stumbling around is pretty implausible. (Especially relevant to sex scene #2. Maybe have MC coach her into a goldilocks situation: Too hard. Too soft. Jussst right).
Other option is to slow this all down quite a bit, which might be a lot easier writing-skill wise. Both options could absolutely use an "educational" slant or learning curve too, plus a bit more initial hesitance or at least caution/concern from male MC. Though I'm sure many would prefer option 1 (quick action) if the dev has enough writing and visual storytelling skill to pull it off with a good retcon/edit. Very much needed.