S Line (TV series)


S Line is a South Korean dark fantasy crime thriller television series released on Wavve from July 11, to July 25, 2025. The series is based on the original Naver webtoon of the same name by kkomabi and was written and directed by Ahn Joo-young. It stars Lee Soo-hyuk, Lee Da-hee, Arin, Lee Eun-saem, and Kim Dong-young. The drama was invited to compete at the 8th edition of Canneseries.
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Synopsis

Set in the near future, where people's past sexual relationships are visually linked by a glowing red “S Line” visible above their heads. A detective, a mysterious teacher, and a girl born with the ability to see these lines navigate a series of disturbing events triggered by the phenomenon.

Cast

Main

  • Lee Soo-hyuk as Han Ji-wook – A free-spirited and handsome detective assigned to a bizarre death case tied to the “S Line”. After wearing special glasses, he’s shocked to see dozens of red lines crisscrossing over his head and resolves to uncover the mystery.
  • Arin as Shin Hyun-heup – The only person naturally born with the ability to see the “S Lines”.
  • Lee Da-hee as Lee Gyu-jin – A mysterious high school teacher whose calm demeanor hides eerie smiles and secrets.
  • Jang Sun as Hyun-heup’s mother – Learns of her husband's affair with her sister after seeing her daughter's S-Line drawings.
  • Kim Dong-young as Oh Dong-sik – Ji-wook’s junior and assistant detective.
  • Lee Eun-saem as Kang Seon-ah – Ji-wook’s niece and Hyun-heup’s classmate.
  • Lee Kwang-hee as Joon-seon – Hyun-heup’s classmate and class president who secretly likes her.
  • Oh Woo-ri as Lee Kyung-jin – A fellow student at Hyun-heup’s school.
  • Lee Han-joo as Yoon Ji-na – A K-pop trainee attending the same high school.
  • Nam Kyu-hee as Kim Hye-young – A classmate who bullies Seon-ah.
  • Kim So-young as Choi I-seo – Another bully.
  • Park Sung-il as Bang Seong-jin – Korean teacher who has an affair with student Hye-young.
  • Woo Ji-hyun as Jung-woo – High school teacher who discovers his fiancée is cheating with a friend.
  • Lee Ka-seop as Oh Jung-min – A serial killer with a history of relationship violence, formerly a math teacher.
  • Park Ye-ni as Hee-won – Jung-min’s ex and Hyun-heup’s new neighbor.
  • Jung Jae-kwang as Bartender – Questioned by Ji-wook while investigating Jung-min.