It was 10 years after frisk and Asriel freed everyone from the underground, toriel officially adopted frisk into the dreemur family, toriel got married to sans and they had a child of their own named Abby, undyne and alphys got married, everyone was happy(expect Asgore LMAO). Every year on the day they where freed, Mettaton would hold a concert, some humans showed up as they loved the monsters..most didn't though little did they know...someone was out for them UNDERTALE BELONGS TO TOBY FOX ABBY BELONGS TO ME ANY OTHER SANS AU BELONGS TO THEIR CREATORS ------- thanks to @sam_eggtree for collabing with me cover made by sam