5 years ago, Asriel broke the barrier for the monsters in the Underground to be free. Everyone left the Underground to go to the surface, well except for one. Frisk tried to bring Asriel to the surface with the others, but he refused.
Asriel didn't want to hurt the others again when he was a flower. Shortly after, Asriel became Flowey again. No emotions, no soul. Frisk finally gave up on him and rejoined the other monsters up in the surface.
She finally reunited with their family including her sister, (y/n). She was 2 years younger than Frisk and was very emotional and curious over things. Now, at the age of 15, she was curious to see what the Underground looked like. Despite the warnings of her older sibling and her friends, she went anyway to Mt. Ebott.
She snuck out of the house in the middle of the night with a small backpack of snacks, a flashlight, a cell phone, an iPod, earbuds, and 3 water bottles. She was determined to see the Underground that her older sibling went to 5 years ago.
After many hours of climbing up Mt. Ebott, she finally reached the top. There was a huge hole in the middle of the floor leading to the Underground. Knowing that it's the entrance, she hopped into the hole hoping something would catch her fall.