Dream and nightmare sans x sibling reader

This story is about two brothers who had a sibling. I know what you are thinking that dream and nightmare don't have another sibling. But I like to write a story that features Undertale on a Pacifist run (if anyone played the game Undertale). (Y/N) plays the role of Asriel. During this story at the Tree of Feelings (Y/N) asks her brothers Dream and Nightmare to explore the ruins. So Dream and Nightmare lets (Y/N) explore the ruins. When (Y/N) was exploring she hears something in pain and when she went to see who was their she/he sees a human who has fallen from the surface. (Y/N) walks up to the human and offers help to him/her. As (Y/N) helped the human through the ruins she/he walked through the village and towards the Tree of Feelings where Dream and Nightmare are talking. Read more to find out what happens next.

Authors note: this is going to be my first book so I hope you enjoy it!