So I'll give a quick summary of Night's or NG's backstory as for y'all to understand why she has 4 versions of herself. I will go more into detail in the future of her backstory, but for now, here's all I'll say. 

Sooo, it all started with a girl by the name of Aiko. She wuz happy. At the age of 6, her father passed away due to cancer. Aiko fell into a state of depression when this happened, and her older siblings, a girl and a boy who were twins, gave her much support. A year later, the twins both committed suicide for an unknown reason, leaving Aiko to take the role as the eldest. After that, her mother married a different man, one who many times took advantage of Aiko. She never said anything in fear. One day, as Aiko was bringing dinner up to her mother, she opened the door and saw something that filled her with fear. Her mother lied dead and bloody on the floor, and her step-father had a knife in his hand, his body covered in her mother's blood. Aiko was furious, and in that anger, she took the knife from his hand and stabbed him to death. At that moment, two of her younger siblings entered the room, and in Aiko's insanity and adrenaline, she killed them too. Once she realized what she had done, she killed herself. For her sins, she got brought back to life as a monster. She knew what it felt like to be called a monster, but didn't know how it felt to actually be one. Soo she a fwiend. One day, as her friend was out, Night (Aiko) went out for a walk. Once the people saw her, they chased her up Mt.Ebbot and pushed her down into the underground. She survived the fall (somehow), and wandered around the ruins. It didn't take her long to notice that it was strangely empty. She wandered into Snowdin, and climbed up a tree when she saw a skeleton with pure white clothes and a red scarf, with a huge ass slash across his chest. At first, they didn't dare trust each other, but ended up as friends. Night had developed feelings for him. Eventually, exactly 6 humans and 1 monster had fallen underground. Both Night and Geno were about to attack, when Night suddenly recognized 2 of le hoomans and da monster. 

AAAAND THATS WHERE I STOP BECUZ IS GETTING TOO LONGGGG