I'm the only one who knows that my younger sister, who is called an angel, is actually a demon. Because of my sister's misdeeds, I was broken up with, so I decided to prove that the angel is actually a demon.

My sister, who appears as beautiful as an angel, turned out to have a demonic nature inside. I was continuously robbed of precious things by my sister, and when my engagement was broken off because of her, I resolved to prove to everyone that my sister's true nature was that of a demon.