S Line (Season 1)

S Line (S라인, 2025) is a Korean fantasy drama series you can watch online on iFILM, directed by Ahn Ju-young and starring Lee Soo-hyuk and Choi Ye-won.

A glowing red thread — the so-called S Line — appears above anyone who has been intimate with someone else. Most people can't see it. One young woman has always been able to, and has kept the ability to herself. That changes when glasses offering the same power start circulating on the black market.

The series blends detective plotting with social science fiction: the hidden ties between people become literal rather than symbolic, and the consequences are hard to contain. Stream all episodes of S Line (2025) online on iFILM.