Signal — Characters & Cast

Initially driven by bitter survival and uncovering his brother's truth; evolves into an uncompromising pursuit of justice for all forgotten victims.

Starts as an abrasive, skeptical profiler moonlighting as a tabloid source who distrusts police hierarchy. As he cooperates with Jae-han, he sheds his detachment, confronting his personal trauma regarding his brother Sun-woo’s framed suicide and growing into an empathetic detective willing to face fatal risks for the truth.

An unshakeable, visceral conviction that police work is about protecting the powerless, evolving into a desperate mission to fix the future even at the cost of his own safety.

Begins as a naive, clumsy patrol officer who refuses to compromise his moral compass. Over decades, he faces severe heartbreak, rampant institutional sabotage, and the knowledge of his own impending death, yet steadfastly refuses to look the other way.

Honoring Jae-han’s legacy and finding closure for cold case families, eventually shifting to actively saving Jae-han once she discovers the temporal transmission.

In the past timeline, she begins as the shy, timid first female patrol officer mentored by Jae-han. In the present, she has evolved into a formidable, fearless Cold Case Squad team leader whose tough exterior masks fifteen years of grief and relentless searching for Jae-han.

Social elevation, bureaucratic survival, and power accumulation by burying police failures.

Rises through the ranks from an opportunistic detective chief to a high-ranking National Police Agency official by fabricating evidence, framing innocent scapegoats, and serving corrupt politicians.

Paternal desperation conflicting with lingering detective conscience.

A detective coerced into doing Bum-joo’s dirty work to pay for his daughter’s medical bills, eventually pulling the trigger on Jae-han in the original timeline. He lives in perpetual torment, ultimately attempting to confess and right his wrongs before being assassinated.