since Niko was a child, she was bullied and abused because of her glitch eye. the only one there to support her was her inner demon. her inner demon could take control of her when she was a child, making both of her eyes black. whenever she remembers her past, hate comes pouring out of her eyes. when she was 18, she fell down the hole after trying to k1ll herself several times. she hides herself from the monsters, and once she saw sans, her passion grew, making her soul the passion soul, instead of a hate soul. after 2 years she finally makes an appearance to frisk when she goes exploring. Frisk then takes her back to sans and papyrus. they become friends. but niko was wearing a bandage when she met frisk sans and papyrus, they've never seen her without it... except frisk, who saw it when her bandage was torn by chara's knife. she made frisk promise that she wouldnt tell the others. and niko can teleport and make force feilds btw :D
song is called HUMANS by KLOUD (song has swearing in it) all code by me