Advantage Tale (Original Undertale AU)

When two siblings fall down to the Underground, the older brother knows the secret of survival down here. He and his sister's determination will keep them alive, he was sure of it. It was their biggest advantage. Well, that and the butcher knife he stole from the ruins. When Frisk is captured by the skeleton brothers, Sans and Papyrus, Chara would do anything in his power to get her back. Using his assumed 'advantage' he hacked through all of the monsters that got in his way. Anything more would spoil the entire storyline. Remember, this is only the beginning! =)