S Line, starring OH MY GIRL's Arin, Lee Soo-hyuk, and Lee Da-hee, has been garnering attention for its thrilling storyline, especially the red line connecting people’s heads. The Wavve original series is based on the webtoon of the same name, penned by author Kkomabi, known for writing hits like A Killer Paradox, Dye Fading, and more.S Line, the series, follows the story of a young girl named Shin Hyun-eup, portrayed by Arin, who possesses the ability to see red threads on the top of people’s heads. The red line reveals the sexual history of a person, as it connects to persons who have slept with them.The Kkomabi webtoon shows the social humiliations that follow as one's personal life is laid out for everyone to see. However, there are some important factors affecting the story structure of the series that set it apart from the webtoon.The drama not only focuses on who a person has slept with; its focal point is which secret relationship a person is trying to hide. The S Line series shows how the red thread would affect others around the people in indecent relationships. This article explores the differences between the webtoon and the ongoing series on Wavve. View this post on Instagram Instagram PostExploring 3 differences between the S Line webtoon and the Wavve drama series1.) New characters and thematic change:According to S Line director Ahn Joo-young in a press conference on July 8, 2025, the drama adaptation was given the liberty to explore the storyline and characters beyond the webtoon. There are several new characters introduced in this series version that have not been originally shown in the webtoon.According to The Korea Herald, Ahn Joo-young stated,“I thought the original work was ultimately a story about people. It mostly focuses on how people change when the lines appear and others begin to see them. I believed the main theme was how new desires emerge in addition to human nature, so I wanted to reflect those changes through the characters via the S Lines. Based on that, we also created new characters.” View this post on Instagram Instagram Post2) Who can see the red lines? In the webtoon, there is a sudden emergence of eerie red lines appearing on the heads of people, revealing their intimate past. The world is then filled with these red lines, creating chaos among people. However, this was limited to one character in the Wavve series, which is Shin Hyun-eup, who was born with this power.Ahn Joo-young, about the visibility of red lines, said,“When we first encountered the work and began the project, we wondered whether it would be realistically possible to visually depict a world covered in S lines. So, we decided to retain the universe but express it in a different way. That led to the idea that only some people could see the S Lines, and that they could be seen through glasses as a medium.” View this post on Instagram Instagram Post3) The mystery of the glassesWhile Shin Hyun-eup can see red lines through her naked eye, some characters in the series use a mysterious pair of glasses and learn about the red lines. At first, they find it confusing and weird, but they soon figure out that these connect people and showcase their intimacy.People who find the glasses and use them soon start to feel a sense of superiority over others, as they know about the opposition. They use the glasses to harm others. Notably, no use of such a pair of glasses has been shown in the Kkomabi-penned webtoon.Meanwhile, viewers may catch up with S Line on Disney+.