Life can change in an instant, and for Hyun-ki, a high school student in Goyang City, South Korea, that change comes in the form of a dangerous obsession. Eighteen years old and studying at Goyang High School, Hyun-ki has a habit of controlling people's decisions, particularly those who pique his interest. He will go to any lengths to achieve his goals, even if it means befriending or entering a relationship with them.

One of his childhood friends is Mun-hee, a handsome and wealthy student who is popular in their school. Another student, Hyun-ae, is known for her beauty and kind personality, and is loved by all the students in the school. She is also friends with Mun-hee.

But their lives are about to be turned upside down when a transfer student named Mi-cha arrives at their school. No one could have predicted the emotional rollercoaster that these four students will experience, including heartbreak and moments of love.