A pretty nice read all around. While the pacing is breezy, we're told enough about the shared history of the characters for the climactic romantic beats to feel justified. The Y2K conceit frames the story in an interesting way – I initially thought it maybe came off as a little abstract and distant, but in hindsight, I like the subtlety of how the possibility of the world ending prompts the characters to discuss various things about their lives. It feels like a smart move to take a premise that has been done many times in this kind of more restrained direction.
Structurally, I'd say it's a choice of mixed success to start with a group scene that splits quite soon into two routes where the main trio never reunites. While reading them, I guess I was sort of missing the banter from the beginning; the protagonist is the least well-defined character, so the dynamic just felt more engaging with all three around. That being said, the two halves of the story do parallel each other in a way that makes sense. It would have been fun for the game to do even more with this – the initial vibe of going to the party probably being the worse choice is not subverted, so there aren't a lot of surprises that would challenge the reader or reframe what they though about the characters.
Apart from that, the writing is generally a bit uneven. The character voices don't come off as too distinct (everyone in this likes saying "fuck" a lot, for instance), which is a little unfortunate when the story is light on characterization and backstory to begin with. We spend a lot of time on learning about the character's hobbies, but the story doesn't go much deeper in a way that would actually inform our understanding of them. Why does Cream like graffiti, and what does it tell us about him? How about Flare and cooking? In shortform work like this, I feel like you have to be a bit more generous with context; otherwise, characters will feel like just a bunch of disconnected traits.