Kind of wary about thinking about starting with a scale of 60 characters, when good stories usually center around like 4-5 different characters, with more characters becoming either completely blank sex dolls, or just a complete stereotypes (Which kind of seem to be most of the characters here).
I played through the prologue, but it honestly felt like the info dump was out of this world. The models look pretty good, but the pacing feels way too fast and the set-ups for certain character traits weren't well thought out. You literally had to go through character sheets for over 20+ characters (I think) with their basic "quirks".Sure it's a prologue, but interactions should be a bit better written for the family, and also more time spent on them. The school is just filled with new character appearances, which I felt was overwhelming for a porn game. For example the character you talk to during class, you left a good impression on her, so there is no reason why she wouldn't show you around the school (She could easily be a class rep, considering that she's supposed to be a nerd, and you could get to know her)? You didn't need to use different characters for that. The character cards you were shown were also too much information. Same with the geek group you met in school (No reason the interaction needed to happen there, at that point and time, when instead you could've been shown different class rooms and again, getting to know the 1 girl). 1 of the "nieces" friends being into you from the start made for an OK scene for a prologue, but again too many characters and a sudden BJ from one of them, with almost no proper set up other than the peeping (I'd say it went too fast).
Though I do wonder why you chose to go with the "Aunt" thing, when the story would've been exactly the same if you made it a "mom" and that she has just married a new guy (Who would be your step-father)? I guess this is the most personal point, but as I just see the exact same story in other games, it feels strange to have her being an aunt now (The tabooness of a mother character is just far stronger imho).
Waifu Academy is quite good about the character balance (Though even that is pretty overwhelming in terms of the pace of the story), it works at most with 2-3 characters at once, you get to know them and their story, you get a few glimpses of other characters, but they're mostly in the background in terms of the interactions. I can understand that WA seems to be one of your inspirations here, but you should start with a focus on less characters, try to give the player some time at home before going to school, a bit of a more focused introduction to the school and 1-2 other characters that go to the school, maybe set up interactions with other characters when you start having a need for those characters (Maybe a bit before the character is necessary in the plot in some way, or if there's a side story you want to tell).
Your story seems to be really frontloaded currently.
A proof reader would also be a great help for you, but that's a non-issue for the time being.
Your models and foundation gets a strong 4/5 (Pretty much as good as a HS game could get, maybe could be slightly improved considering that WA does look better for me, but still this isn't an issue).
Your story, characters and pacing are 2/5 or 1/5. You just started off, so it should be easy to fix.