I do not own Undertale! I am not using anyone's work. I am making this from MY OWN thoughts. THANK YOU! This story starts right before Frisk (Girl in this story) falls into the underground.
"Hey look!" Kids were running towards Frisk at a great speed. She tried to avoid them but some more kids blocked her path, preventing her escape and leading to the inevitable...
This has all happened before, repetitively. She had tried telling teachers and her parents before back when it started but they didn't do anything about it and still refuse to do so. It was obvious that when the bullies new they were never going to get in trouble, the worse it became.
"Hey, I'm bored! Lets go pick on some other kids pathetic kids who can't speak! HA HA HA!" They left Frisk laying there. She was bruised, and started crying out from the lingering pain of the punches and kicks she had just received, after they disappeared. She would go home, talk to her parents, head for her room, and collapse on her bed. She used this time to think to herself about the day. The same routine she had done every day, for the past two years. Later that night, Frisk laid in bed staring out her window. Tending to her bruises, she thought about every time she kept finding herself in that position. Then she remembered something they said once.
"those who climb the mountain never return." And at this point, it was worth a shot.
The next morning, Frisk awoke, got dressed, went downstairs to eat breakfast. Then she left. Nothing was out of the ordinary there, but instead of heading to school, she headed for the mountain. It wasn't a short walk, but maybe getting to the top of the mountain would be worth it.