Rainbow Eyes

An affluent entrepreneur is found brutally slashed more than 20 times in his blood-soaked apartment. The killer leaves little incriminating evidence, making the case puzzling. A strand of the killer's hair is recovered, giving investigators a crucial lead about the suspect's gender and blood type.

Police determine the killer is male and AB-blooded from the hair evidence and scene traces. This narrows the suspect pool but leaves investigators without a solid identity. The investigation shifts into a forensic and profiling phase.

Kyung-Yoon's personal life collides with the case when his girlfriend asks to break up, claiming he loves someone else. She references another person and sounds heartbreakingly certain in the moment. The emotional strain complicates his ability to focus on the investigation.

Shortly after the first killing, a second murder occurs with a strikingly similar method. Investigators note the pattern linking the two crimes beyond mere chance. The city grows tense as police race to identify a serial-like threat.

Investigators uncover that both victims were stationed at the same military base years earlier. Before discharge they were transferred to another base along with a third man named Jong Ha. The military tie suggests a personal motive rooted in their shared history.

The police suspect Jong Ha could be the next target or the killer himself, given his proximity to the trio. Clues about their movements are tracked, but the trail remains murky. The case expands beyond the city into the base's past.

Kyung-Yoon learns that his old friend Yoon-Suh, who shared the base, shot himself. The tragedy hints at deep trauma and a web of secrets surrounding their unit. The discovery intensifies the emotional stakes of the case.

Flashbacks reveal Yoon-Suh as gentle and effeminate, whom Kyung-Yoon protected from bullies. Kyung-Yoon tells him to man up, a moment born from fear and shame. The memory foreshadows motives and complicates how the audience interprets subsequent events.

An old military contact reveals that Yoon-Suh joined the service only because someone told him to man up. He was abused and raped by the trio before discharge. The revelation reframes the killings as a response to abuse and power rather than random violence.

Kyung-Yoon confronts Jong Ha, who angrily dismisses Yoon-Suh and mocks his suffering. The confrontation escalates into a brutal scuffle, leaving Kyung-Yoon bruised. Eun-Ju phones to report that Jung Ho was found dead, adding a new layer of urgency to the case.

Eun-Ju discovers a secret passage at the first crime scene that leads to the kitchen, where a cook with a weapon similar to the murder tool tries to flee. He is captured, linking a domestic figure to the crimes. The discovery broadens the suspect pool to include someone from within the killer environment.

A key clue prints out the killer's new identity, which turns out to be Kyung-Yoon's girlfriend, the person he planned to marry. The revelation unsettles Kyung-Yoon and forces him to reexamine loyalties and love. The lines between detective work and personal life blur.

Kyung-Yoon confronts Yoon-Suh, who admits that she killed the victims. They flee on a motorcycle, triggering a tense police chase. Kyung-Yoon grapples with his forbidden love for Yoon-Suh while coming to terms with his own past actions, including a kiss during a prior confrontation.

It is revealed that Yoon-Suh did not kill anybody, while the cook killed the rapists and the singer he loves, confessing his feelings as he murders her at the end. Eun-Ju had known that Kyung-Yoon played a role in Jung-Ho's death but keeps silent out of loyalty. The true killer identity shifts to the cook, ending the mystery on a tragic, melodramatic note.