I must say, this is the best Honey Select game I've seen and generally one of the best titles on this site. All the more impressive in that it was pretty unknown to me until today. It's not a title I see people mention when talking of the best adult VNs available.
It's not perfect (nothing is) but it's solid.
I'd recommend a couple things to make it better:
1. Remove or improve the door dream section in chapter 3 (iirc).
2. Going forward, definitely make the option to have the girls go with other men. Not for the sake of NTR or any fetish but for consistency. The possibility has been more than hinted at already so to remove that OPTION would be pretty lame (and weird, given the story). Keep that angle.
3. Do not forget about the side characters like so many VNs do. They introduce a new girl and very often they're only there to fuck once and never see again. It's a cheap way to add sexual content without spoiling the main girls too early.
Make sure the friend stays in the story, as well as the other classmate (that was basically a meet and fuck character). Don't ignore them.
Other than that this is a VERY solid title. Good characters, funny in some moments and truly a bit scary in others. Fear is a hard thing to get across in any VN and few do it well. This title had a couple locations/scenes that do a decent job of it.
Keep up the good work!