S Line

Hyeon-heup, born with the ability to see the 'S lines' that reveal people's sexual connections, faces deep personal tragedy due to her power. Isolated by its consequences, she withdraws from the world and lives in solitude for years, until strange events make her return to society.

Hyeon-heup enrolls in Bangju High School after getting a strange text. There, she unexpectedly reunites with Seon-ah, a former classmate from middle school and the niece of Ji-wook.

After a rooftop incident leaves Seon-ah in a coma, Ji-wook teams up with Hyeon-heup to uncover the truth, driven by guilt. Meanwhile, teacher Jung-woo ends his engagement after catching his fiancée cheating, only to discover a mysterious pair of glasses on his desk.

Ji-wook investigates Seon-ah’s case but doubts Hyeon-heup’s theory about the S line. School secretary Mi-seong stumbles upon the infamous glasses - only to be consumed by jealousy when she notices another woman tied to the man she secretly admires.

Ji-wook discovers a pair of glasses in a bloodstained bathtub, validating Hyun-heup’s story. With the glasses, he begins probing sexual assault cases and suspects that someone connected to Seon-ah's S line may be responsible for what happened to her.

The mystery of the S lines comes to a dramatic conclusion as loyalties crumble and unexpected truths surface. Hyeon-heup must confront choices that will change lives forever, along with the consequences of seeing and being seen in ways never imagined.