"Seoin didn't commit suicide. She was murdered." A photographer who captures the world through a camera lens despite suffering from a visual impairment. She investigates the death of her younger sister, Park Seoin, who lost her sight before her but lived as a successful ceramic artist. She struggles to uncover the truth hidden behind a death disguised as suicide. Though she cannot see, she relies on people rather than tools. A woman in her early 30s.

"Unnie, why won't you understand my way of doing things?" She overcame her visual impairment and succeeded as a ceramic artist, but met a mysterious death. She shares the same face as her twin sister Park Seojin, but the texture of her life and emotions were different. A woman in her early 30s.

"I'll be your eyes." He becomes the eyes for Seojin as her vision gradually fades, tracking the truth of the case with her. (Twist: The identity of the kind 'helper lady' who hovered around the blind Seojin is actually Detective Lee Dohyuk in disguise. He has two personas.) When Park Seoin lost her sight completely, he approached her to become her 'savior' and helper to gain recognition. However, when Seoin planned to undergo corneal transplant surgery to see again, he was seized by fear and possessiveness that she would leave him and no longer need him once she regained her sight. Ultimately, he murdered her and staged it as a suicide. A man in his late 30s.

"The way you take good pictures of me, Noona, that's definitely love." Due to his obsession with Seojin, he violates restraining orders and later cuts off his electronic ankle monitor to flee. He stalks Seojin, providing unpredictable energy and anxiety. Kim Hyunmin's criminal record and history of fleeing become the decisive reason Seojin leaves her home at the police's suggestion to visit her twin sister Park Seoin's house for a while. When Seoin is found as a mysterious corpse, his history serves as the justification for Seojin and the police to suspect him as the prime murder suspect. A man in his late 20s.

"It would be best if you meet with us quickly. Where are you now?" A protection detective who guards Seojin from her stalker Kim Hyunmin, who is obsessed with the protagonist Park Seojin with persistent madness. While accompanying Seojin to Park Seoin's house, she is the first to discover Seoin dead, hanging in the basement. She is a veteran detective. A woman in her mid-40s.