English is not my native language, so I hope you can excuse my poor grammar.
I like your game so much!
Artstyle is not just beautiful and girls are hot, but it feels fresh and alive, not like some souless wannabe realistic backgrounds end other similar things which plague not only NSFW genre games but many of the more common titles which graphics looks similarly boring.
The general setting is pretty interesting and nice, especially for your type of game: it flashed enough, so even people alien to Harry Potter books could understand it inner workings, yet it didn't bore you with too much exposition. Our main character is also a good change of pace - many NSFW games make you play in the range from jerk who use vulnerable girls to serial rapist, so it is very nice to be a decent man genuinely building good relationship with girls, it's actually very nice being good and helping people!
Your girls also work very good not just as eye-candy but as whole characters themselves: they all feel different not just by bust size and type of visual characteristics, which they also are - it didn't feel like the cast are copied and pasted model looking big boobs and ass template, but from the point of own personalities and backgrounds. It feels rewarding speaking to them, knowing them more and understanding them which gives attitude not of simple porn game where you skip text to get to bed scenes but of good quality visual novel with minimum of filler text which amount to nothing. You can actually feel connected to characters despite there being not much content for now - but many titles can't get even this despite being full length games.
Minigames are another game point which I like. They are not too hard for the player who would feel like he needs some handouts or cheats yet they are hard enough to feel like games and not absolutely mindless grind just for the sake of it - it is good. Difference in the mechanics between sawmill and mine are nice, it's helping to avoid staleness in this type of tasks. Magic system has the same advantage - it helps it rare moments when it occurs to make gameplay more active and diverse while giving player a little challenge.
In my personal opinion, such a combination of good-looking yet no shallow characters to have love with and engaging enough yet not too grindy gameplay outside of dialogue is a path to success for any NSFW title, which could potentially lead to flourishing community and chances to even get a full-fledged series. Many games couldn't do it: LN types are commonly being played through few times for the sake of sex-scenes alone and then forgotten, while such big projects like Subverse failed to find suitable balance: while getting pretty nice space shooty gameplay they failed to deliver sex scenes adequate for both cost of game and its space battles level. Yet, I see that you're craving the right path for yourself and I hope that you will get your game to gold and make others take your work as guiding for their endeavors.
But I wish to be honest wanting to help you with my feedback, I understand that words of only one man, but i still like to ask you to at the least think about what I can say.
There are few weak points of your game, but I think the few sex scenes are one of them. Please don't get me wrong: I think that situations are good (maybe except the cave one, but I still think it was a little bit funny) and graphics too - girls looks amazing in all of them, but animation is the culprit. I think the main gripe is with Lillian second scene - in the end, it is just too fast. And I think it is not just preference thing - it is just limitation of animation type which you chose. I understand that it feels like I demand additional work for an already big project, but please think about not making such a fast animation - it looks not very good with yours limited amount of frames per second, maybe instead of just making scene faster you could on final stage change a pose a little? So that it will pour new fire in it, maybe in way of different hand gestures (you know, such passion ones like hug over neck etc) or face expressions so it will change not so much for requiring too much of rework. But on the good note i must say that small details in animation are very good - like girl's blinking and hair swing, it makes it a lot more lively and attractive!
Also, other world gameplay is a very good addition - it paves a path for great potential, yet I urge you to not stop now i way of its mechanics. I'm not speaking of any visuals of it, they are actually ok as they are, it's just mechanics. For now, it feels just too shallow, so in the way it appears grindy. But you're actually not the first who pave a successful way in that field - there are other games who used similar mechanics, which could help you find ideas to enrich your own. I think the most popular one is Fate Grand Order - gacha with similar styles of battles. Being a gacha it grindy by default, yet its gameplay being simple still posses desired depth to being interesting, possessing low entry level and decently high for that type of game skill ceiling. Another one would be Darkest Dungeon and Iratus, especially the second one. They have even more depth, and if you can provide at least a little of what they can - people would literally play the game not just for girls but for other world regime. But despite what I said about it - just continue to work on it, please don't leave it as it is, you already have a great base! Maybe you can let us recruit some creatures which we fell in battle in our team? Even if we could not have them as full-fledged characters in main word they still can stay in academy, making it more lively, and it would be even better if we could add them in team to battle together!
In the end, I want to say that I liked Joyce very much! She looks very cute and hot with ponytail and I like her playfulness! And it also very cool to see you add catgirls like Audrey, they are very cute! I hope we will see more of them in the future!
Hope that I was at least a little helpful with my feedback, thank you again for your great game! Will definitely buy when you release on steam! And sorry for bad english!