Several snippets of text suggest or support the idea that “Undertale” is an unfinished/unreleased game Asriel made. This makes sense in some ways; the characters are all younger, matching the period in which Asriel was living at home working on his game. Inversions like Catty and Bratty being best friends instead of feuding rivals seem like appropriate changes from someone so soft-hearted. Toriel and Asgore’s separation is given a much more dramatic context and explanation, and in this scenario, Asriel places the blame indirectly on himself.
Some aspects don’t fit as well. Deltarune implies that Asriel probably hasn’t met Sans or Papyrus, and considering he put Kris’s friends (the monster kid and Snowy) in the game, you’d think he’d have put some of his own friends in, as well. Or maybe he’s making the game for Kris, as a way of dealing with what’s happening in their family? Thus the emphasis on figures like Undyne (who was just then replacing Asgore in the PD) and Alphys (who replaced the just-deceased Gerson in the school)? Then what of the skeletons, or the choice to reach an ending through maximum violence? There’s no answer; this is just a what if.
Chapter 1 is board and card games, while chapter 2 is the internet. Chapter 3’s gotta be TV then, right? TV commercials and yet more anime references seem inevitable, but what were the shows Susie flipped past during the sleepover? Any of those could give a clue as to what kind of environment we’ll be exploring next, and we know Undyne should be on her way to the house, so she’s likely to feature in the next one as well.