Twins who like to play pranks on others and are innocent in nature, they don't seem to understand the consequences of their actions. However, they're actually quite powerful and can hold a grudge for a while.
They don't like to speak a lot, so it's hard to befriend them. They prefer to communicate with each other telepathically with each other or in an ancient language only they seem to know. When they do speak, they refer to themselves in third person a lot, use the word "we," and tend to speak simultaneously. Those who do become their friends find that the twins are fiercely loyal and will do everything they can to protect them. They are often lonely, as many are afraid of them, even though Yin and Yang don't know why. The two like keeping pets to ease the loneliness.
Yin has long black hair with a large white stripe down the middle. She wears a black version of Miku's outfit, white headphones, a white tie, and her eyes are two different colors: the left one is black, and the right one is a light blue.
Yang is completely opposite. She has long white hair with a black stripe down the middle. Her outfit is a white variation of Miku's. She wears black headphones and a black tie, and like her sister, her eyes are also two different colors: the left one is light blue and the right one is black.
Here's a link to see a video of them, made by their creator (not me, unfortunately...but I got her permission to post them here!):
http://www.youtube.com/watch?v=bIZAu58UuJI&feature=channel