Okay well I'm not sure on what to say exactly but i'll try anyways!
First of all your art style definitely caught my attention. I like the different textures and saturated colors are my weakness. I died at that pinched joey wheeler face marina was pulling at Sidney. Like, how does anyone continue a conversation with her with that face being made? lol Though I feel like there's something off with her eyes and i tried to figure it out since I didn't feel that way about any of the other guys' eyes and I think its the size in comparison to her other features (mouth/nose). that may or may not be it.
The story is pretty interesting, though its nothing dramatic I think the way you've made the characters will be the standout thing other than the art, oh that and the cursed chemistry theme. Like I hate science with a passion so the story was that interesting for me to still try the demo anyways! I got like a 2/3-5 for the quiz so idk Marinas just going to have to fail in the full version with me playing.
I was looking through the game's topic on the forum and I didn't know this was set in Hawaii but it makes a lot of sense now. (floral shirts for all) As for the cg styles and such I say go for whatever you feel like or what feels right, even mix it up if you want. I know a few VNs that have different styles for sprites/cgs/ect i dont see the problem!
Like I said before the dynamic between the characters are interesting enough to make you wonder how the whole mutual tutoring thing will turn out and whats up with the underlying drama going.
Good luck with your finals!