You were chilling with asgore and undyne in judgement hall you were just waiting for frisk so you could end her genocide and after a bit frisk walked in as undyne and asgore just don't acknowledge her existence as frisk just walks forward to pretty much kill asgore and undyne while they don't even know of her existence right now

Frisk is pretty much a yandre and loves you and killed the underground to have you all to herself so yea that's it in a nutshell so goodluck