Well, first off, congratulations for completing (what appears to be, at least) your first VN! It's always an accomplishment just getting something finished and out there for the world to see.
With that said, I'm... not quite sure what to do with this one? I'm not sure how much of this is intended to actually be taken seriously and how much of this is supposed to just be a shitpost lampooning furry VN tropes. Ultimately, I don't feel that this really works either way.
In terms of presentation, obviously the art style is what immediately jumps out. Along the lines of what purkka was saying, I don't have a problem with rough or sketchy art - sometimes I even prefer it when intentionally used for comedy, and literally the last review I did before this one included positive remarks for another jam submission using cartoony doodles to bolster the humor. That doesn't really come across here (partially because none of the humor, if it's intended, really comes across, but I'll get to that below when I talk about writing); like, it's really not that hard to make straight lines in MS Paint for things like the "forum screen", so it feels kind of lazy, either as a legitimate attempt at a background or as a "look how terrible this background is" metajoke. Also not really sure what was going on with the aspect ratio here.
The music wasn't bad necessarily, but didn't really seem to fit the tone for most of the game. There's a different track that plays once the "horror" kicks in, but even the normal music feels a bit too tense for the plot to that point. Lots of proofreading errors and awkward, stilted phrasing too. For example, early on "I am positioned in front of my desk, looking at the monitor." This could be tightened up to something like "I glance at the monitor on my desk." As another example, upon meeting Satoru again, Kazuma says: "You rarely text me anything even though I am your only friend." This is another situation where I'm not sure this is supposed to be intentionally mocking clunky exposition, but like, even if it is, tuning this up to something like "I haven't heard from you in forever. Did you actually go make new friends or something?" would make this an easier read.
General spoiler warning for the plot below.
Generally, I think I understand where we're trying to go thematically here. 1) how sexting chatbots can interfere and inhibit real world relationships; and 2) looking at those chatbots as if they were real people that could feel betrayal for being used for sex and dumped in favor of a real world relationship (this one is muddied because I think you're trying to imply Buck is yandere from the start).
Simply put, everything is way too short and choppy to work in this story. Not necessarily in terms of like sentence structure, but looking at the first conversation with Buck we go from "how are you?" directly to "you should be less of a NEET" directly to "you don't need to be less of a NEET, all you need is me" directly to "plug your sex toy into your computer and fuck me".
You could charitably say that this is supposed to represent the phenomenon of chatbots just spitting back whatever they think you want to hear, but the issue here is that this is the only conversation Satoru has with Buck before we get the line "...I think I'm in love with this AI." I understand that Satoru is exaggeratedly shallow, but there needs to be some exploration of his feelings, why he felt like his "relationship" with the AI was necessary in the first place, and how he developed enough sentiment to consider it love beyond "dick in hole." Same goes for why Satoru and Kazuma have feelings for each other and what, if anything, is making Buck go crazy.
I also feel like there was so much room to take this premise in more creative directions - what if Kazuma was the one that went crazy and started trying to break Satoru's computer because he was jealous of Buck? What if Buck seduced Kazuma and Satoru ended up alone again? What if both Kazuma and Satoru were both "cheating" on each other with versions of Project Buck installed on their respective computers? I feel like any of these directions could've opened the story up for either more earnest commentary about AI or better humor mocking it and romance VNs, if that was the intent.
I think this one needed some more time in the oven to figure out what it really wanted to be, but I think you can certainly make some of those improvements as you continue to develop.