S Line

Hyun-heup, a girl who was born with the ability to see the S-line that indicates sexual relations. Because of this ability, Hyun-heup's family faces tragedy, and Hyun-heup becomes a reclusive loner for a long time. Then one day, a series of suspicious murders occur around Hyun-heup, and Hyun-heup uses his ability to see the S-line to track down the case...

Hyun-heup goes to Bangju High School after receiving a mysterious text message. There, he reunites with Seon-ah, a middle school classmate and Ji-wook's niece. However, Seon-ah is a victim of bullying from bullies. One day, when the bullying from bullies reaches its peak, Seon-ah discovers a mysterious pair of glasses in her locker...

Seon-ah falls from the rooftop and falls into a coma. Ji-wook cries out in self-reproach and anger, and cooperates with Hyun-heup to find the culprit. Meanwhile, Jung-woo, an English teacher at Bangju High School, witnesses his girlfriend's affair before their wedding and breaks off the engagement. And soon after, he finds a pair of glasses on his desk...