Alright, so I've played through Ted's route (special ending) and half of Kurt's route and I've got some strong opinions to share, so here we go! (Disclaimer: These are my personal opinions and you're free to disagree with me. I'll try my best to be objective and any criticism I offer is meant to help further improve those points in the future.)
The good things first:
1. The art! I really loved the amount of detail and care you've put into the character design, I've played a lot of otome games and this one is definitely in the top 3 art wise. The colouring was very 'gentle' and gave me a calming feeling while playing.
2. The music! I don't know if the songs were original or not, but they always fit the atmosphere very well.
3. The idea! I love love love mystery, but I also love slice-of-life college stuff, so both in combination should've been perfect. I deliberately used 'should', but more of that later. Even if the execution was in some points lacking, you definitely get props for original concept.
4. The GUI! Not much to say here - very accessible and easy to use!
5. Game flow! I liked how the routes diverged only in November, meaning that you could build relationships with all the guys till then. Even though naturally, you focus on one guy from the start, it's nice that Nicole didn't appear isolated during the game and still had interactions with everyone. I especially liked the fact that there was so much Darren in Kurt's route because they were roommates - it makes the interactions seem much more natural. The number of events in-between stat raising was also adequate, it didn't make me feel too bored.
The things that could use improvement: (I'm not saying bad things because they weren't bad per se, just... frustrating, I guess? Because I've seen it done better and I know it *can* be done better.)
1. CGs. (Guess I'll start with the smaller things first because I'm not quite sure how to express the rest... English isn't my native language, so sorry for that^^) Anyway, for a paid game the number of CGs per route is definitely too small. I didn't get any CGs in either routes till like, December, even though there were definitely CG-worthy moments before that, like where Nicole visits Ted's room or Kurt and Nicole browsing Nicole's blog. Sorry but even in free games there were more CGs than here and that's definitely saying something. In this case, I'd even say you should go with quantity over quality if you feel pressed for time because collecting CGs and looking at them later in the gallery is, for me, one of the most rewarding parts of playing otoge. If the background wasn't super detailed, I wouldn't mind as long as the characters are pretty. Also, I don't know if that's the case in every route, but in Ted's route I found the first CG - where they're arguing in the shop during the block party - not fittingly placed at all. I mean, they're shouting at each other for God's sake, but then all of a sudden in the CG they're totally happy while in the textbox the shouting continues? Come on. Either toggle the CG a bit later or make multiple ones that transcend with the scene. In a visual novel, of course I'm gonna rely on the visuals to tell a big part of the story so if story and visual don't match? It really disturbs the experience. In Lucky Rabbit Reflex, for example (I'm gonna be referencing this game a lot because the genre is very similar to your game - stat raising romance - sorry in advance for that), there's a CG of the player asking the guy what kinda girl he likes. Obviously, he likes the player but won't admit it, so while he dances around the topic, his eyes in the CG flit back and forth, looking to the player and away. It's such a minor detail but adds so much to the atmosphere! And it doesn't take much time to draw since all you have to change is the eye placement.
2. The dialogue. I've read it in other reviews of this game as well and I have to agree - at some points, rather often actually, the dialogue doesn't sound natural at all. Unfortunately I forgot to take screencaps while playing so I don't have any direct examples, but I'll try to generalise... You tend to use a lot of words that aren't used in teenspeak anymore, and that makes it sound like you're trying to forcefully sound 'hip' and 'cool', which... well, if you've ever had your parents try to do that when you were a teenager, you probably understand the feeling that dialogue gives off. In Ted's route, some of them are attributed to his accent, which I understand, but on the other hand, with the existence of the internet and the fact that everyone is exposed to a variety of accents through globalisation/migration and simply through watching stuff on the internet, I don't think local dialects are as pronounced anymore, especially with teenagers. I'd rather say that there's more or less one common 'teen English' which is 'in' and everyone tries to imitate it (see lol, yolo, dude, bro, and so on) and those words you had Ted - and even occassionally Nicole! - use were dialects spoken by the older generation. No teenager would try to imitate the way their parents speak, that would be way too 'uncool'! Especially Jeff's speech was way over the top, he sounded like some kind of comic book villain. And that would be fine, mind, if the game was written in a comic book style! But if you aim for a realistic, slice-of-life feel, which I got the impression you were trying to do, then you've got to make your characters sound realistic as well, and not like stereotypes. And that brings me to my next point.
3. Characters. Well, they weren't completely unbelievable. I actually did like all of them, even Jeff. But only because from the beginning on, I forced myself not to take the the game as a serious game but rather a comedy game. In that mindset, the characters' quirks and unusual sounding dialogue made sense since I could interpret it as a comedic relief. However, that point of view clashed with the very real and serious conflicts you introduced later in the game. Having Jeff still sound like a comic book villain during the final confrontation in the abandoned building, while he was being faced with the very serious crime of kidnapping and performing experiments on girls, just didn't sound realistic at all and somewhat ruined the scene. Similarly the way Ted kept being all overly serious and 'tsundere' even in supposedly fluffy and romantic moments. It just felt like every character's personality revolved too much around their main stat, which made them too two-dimensional, lacking dephth. Again, that would be okay in a mainly comedic type of game because you're not *supposed* to take those characters too seriously. But in this type of game, the characters seem too shallow. I also wished for Nicole to have a bit more character development over the course of the game depending on which route and stat you chose. Like, on Ted's route, she's dilligent and hard-working, right? Then have people complement her on her good grades! Have her make the smart choice and tell someone about the threats! In Kurt's route, she's zealous but more into sports than studies, judging by the activities you have to do to raise your stats. Then, have people tell her how fit she looks and have her act more rashly, let her fail some exams! It would add *so* much to the experience, making it easier to understand her choices. And if you say that would take too long/make the game too long, well, all those examples I brought up are from Lucky Rabbit Reflex, and that game costs just as much as yours while taking place over the course of a whole school year instead of just one semester! I'm just saying, if I pay money then I expect to get that money's worth back and I doubt I'm the only one.
4. Inner monologue vs action ratio. This one is a bit hard to explain but I'll try. Since this game is part dating sim part visual novel, of course I expect a lot of the ongoing action to be shown through, well, action - as in images on screen or dialogue. Instead, in this game I found the amount of Nicole's inner monologue, and of descriptions in general, to be disproportionally large. Why not show something instead of describing it in text? Similarly, why not have Nicole say/think something directly instead of describing it via first-person narration? Example: When Ted's Dad is introduced - actually, when every character is introduced - I remember Nicole going on a several lines long rant, describing their looks and how hot she thinks they are in detail. Why? The reader can perfectly well see the colour of their hair themselves! Instead, why not have her think something like "Whoa! DILF approaching at 12 o'clock!" and then express the rest in actions instead of musings? Like, if you have her stutter and be accidentally drop something while blushing, then force a laugh and apologise, to the reader it will be perfectly obvious she finds the other person attractive. You don't have to explicitly state in her inner monologue that she does so. Sometimes, less is more and it's better to have the reader see how the character reacts and infer the meaning for themselves instead of just bluntly stating it. Similarly with things like jokes. You don't have to have Nicole say "I chance a joke" or something (I don't remember exactly what was written). Instead, just have her make the joke and then clap her hand over her mouth or think "Oops". From that, it's already obvious that she's anxious whether the joke will be well-received, but it doesn't sound as boring as when stated bluntly. What I mean to say is, I think you should rely more on visuals and action/reaction instead of description.
5. Difficulty. To be honest, I'm not the biggest fan of stat raising. Mostly, I play choice-only VNs, so when I do buy a stat-raising game, I'm in for the story. I don't mind the stat raising as a means to an end, but in this game I found the difficulty level to be so high that it was very frustrating. Even on the easy setting, I was anxious till the beginning of December that I wouldn't be able to raise the stats enough for the special ending. I did manage it in the end, but I just barely made it and the fear that all that time could've been for nothing just made me needlessly stressed during the game. It wasn't about figuring out the right gifts or stats to raise, that was easy, but simply raising over 900 of the specific stat and 999 clues was such a huge hurdle that for me, the game felt too difficult. Maybe it's because I don't play dating sims very often, but it's not like your game should be aimed at 'veterans' only and anyway, in the other 2 such games I played (Lucky Rabbit Reflex and RE:Alistair) I didn't have any problems reaching the goal once I knew which stats corresponded to which boy and which gifts I had to give. If you wanna make a hard mode for people who like stat raising, go ahead, but if you say there's an easy mode, you should make it easy accordingly. Or simply make cheats for players like me, who're only in for the story, I wouldn't mind that either.
6. Plot. I have already briefly touched on aspects of this point in my other points, so I'll try to be brief. While I really liked the idea you had going, I found the execution to be very lacking. I had the feeling that you couldn't quite decide what type of game this is supposed to be and in the end, you just mixed all the elements together without finding a proper balance. There are elements of mystery, of slice-of-life, of comedy and of romance but all of them just don't fit very well together. I'm not saying that they're inherently incompatible, it's just that you jumped from one to the other so quickly and without a main thread to bind them all together that in the end, the game was neither here nor there. I'm being very abstract, sorry. I would've thought that the main focus of the story would be mystery (*serious* mystery, with maybe a few comedic elements but not with comedy as focus), as it was advertised as such. But, in that context, a lot of Nicole's choices just didn't make any sense. No sane person (of her age) would just run into an abandoned building, alone, without any weapon and without contacting anyone else. It would've been fine in a comic-style game, because it's supposed to be over-the-top for the sake of laughs, but the setting you had set up before that didn't allow for that. Nicole has loving parents, is fairly rational and smart (at least she's supposed to be in Ted's route - and here we again come to the point where stat decisions should influence her character) and has a boyfriend she repeatedly describes as reliable. In a mystery/slice-of-life oriented setting, her decision makes no sense at all! Maybe in Kurt's route, yeah, but not in Ted's. Also, the whole mystery thing - again, it seemed more fitting for a comedic story than a realistic one. Honestly, I suspected Jeff to be the culprit from the very start just because he was the stereotypical villain, but I kept hoping until the end that maybe it was someone else altogether, like idk, Nicole's roommate or something, because in a mystery oriented game no way should the first guess be the correct guess, right? And the whole showdown in general was just way too unrealistic for a not-comedy setting. But the game wasn't mainly comedy-oriented either because of the conflicts and decisions the characters had to face, because of the conversations they had and because, well, sorry to say it but the jokes you *did* implement just weren't that funny. *shrugs* So I hope you understand what I mean when I say you tried too many things at once but didn't really have a 'red thread' to follow through the story.
TL;DR: In conclusion, I'd say that the game has a very promising foundation but what you made out of it could use some more work. Especially for a paid game, I'd expect much more professionalism story-wise and character-wise. I admit I probably wouldn't have bought the game had it not been on sale and I don't think I'll be buying any Winter Wolves games in the near future. But I'll definitely be keeping an eye out for your new releases because I really do think your work shows a lot of promise, it just needs some more polish and experience.