The most outstanding issue is probably the writing being in need of another proofreading pass and, in general, not feeling like a perfectly natural fit for the medium. Besides all the missing periods, basically every textbox is exactly one sentence long, which makes the pacing feel relentless – you really want to use longer and shorter lines as appropriate to set a rhythm just as books would use paragraphs of varying length. I appreciate the custom touches in the UI, but coloring dialogue differently for each character instead of using name labels is a pretty annoying choice that also hurts accessibility.
As for the story itself... I can't say I had a bad time on the whole, but I think the soap operatic antics and all the wild twists left me more baffled than emotionally engaged. Both endings feature over-the-top plot beats that it would be hard to buy into regardless but that especially suffer from lack of setup in the form of subtle characterization to emotionally ground the characters. Being a bit coy about the extent of the protagonist's obsession and true intentions makes for a shocking surprise, but it also means that the reader gets very little time to settle into what's actually going on by the time it becomes relevant. Also, I feel like a lot of the dialogue in particular betrays the author being quite young, which harms the believability of a story about aging and living with grief – in contrast, though, the instant messages do come off as realistic.
The art feels like the game's strongest suit: the sketchy style is good to look at and conveys a distance that makes the story a bit easier to read as purposefully exaggerated, and I like that there's a consistent color scheme across the sprites and the photo backgrounds. Strong cyans and reds are used in a thoughtful way, too. Congrats for releasing your first VN!