Sang-eun is a beautiful 20-year-old girl who is mentally challenged. One day she happens to meet a boy and deludes herself to think he's a beast under the vicious spell.

Today is righteous Chae-young’s first day of her transferred school after beaten a bully to nothing. Despite the dad’s warning, she saves her classmate Jong-gu from bullies again. Fascinated by her, Jong-gu asks how to be strong like her.