Sadness.

Mirror Image.

Two images, move in sync.

They smile, they laugh.

They are pretty, and they are happy.

These two images look perfectly the same, but are not.

They are as similar as yin and yang. 

They hate each other, and in the dark they glare.

These to images.

These two sisters.

They wish and plan one another's death, hoping on day that one will disappear.