[You're Not Alone] Underverse Cross Sans X Reader

You were a kind human who has a brother named Frisk. You and Frisk always get along until both of you climbed up a mountain. very curious if the legend was true or not. "(Y/N)!! Help!!" You looked towards where Frisk was. He fell into a hole as you jumped in to help him. Both of you landed on the ground with flowers c...