A murderer, a monster, a sinister devil. That's what he is. A strong and sweet and kind outer, a sinister and monster-like devil inner. Your bestfriend is exactly that. Jung Daehyun is exactly that. But you didn't know that. You have fallen into Jung Daehyun's trap. A powerful monster's trap.

An innocent, pure, angel. That's what she is. A sweet and kind and nice outer, a pure and innocent angel-like inner. You are exactly that. Kim Eun Hae is exactly that. But you didn't know how far your powers can go. You didn't even know you had powers. You also fell into Jung Daehyun's trap.

He had a mission to accomplish. Ever since he was little. Trained to be a monster since he was a kid. His mission was to kill the innocent girl. The girl that the prophet has said to be the one holding the pure and kindness in this world. Kill her and let the evil overcome the world. He learned everything he needed about her. Kim Eun Hae was exactly that innocent girl. 

Jung Daehyun, who was 7 years old, met Kim Eun Hae, who was 6 years old. She was building a sandcastle with whatever she had, a bully comes and kicks the sand into her face, she wipes her face with her hands, and smiles at the bully and says "no need to apologize. I forgive you! Let's play together now." The bully calls her "stupid" and "crazy" and "ugly" although she was nowhere near ugly. Daehyun was very smart for a 7 year old so he goes over and says "NO! She's perfectly beautiful and smart. Those words you just said, you must be describing yourself because you're exactly that!" to the bully. The bully runs off crying.

Eun Hae smiles at Daehyun and plays together. They go to the same school but they never really met each other at school. Turns out Daehyun is in a grade higher but he's always sleeping and ignoring whatever people said, and Eun Hae was a grade younger and always studying. They started talking more in school and outside and soon became best friends. Little did she know that her best friend Jung Daehyun is a sinister monster and that he's out to kill her.

Credit to F R O S T Y for the poster !