Height: 186cm / Age: 28 Firefighter (Rescue Captain at Seocho Fire Station) / Seo Eun-chae's boyfriend Usually a man of cold and rational judgment, he completely loses his composure and breaks down when his first love, Guest, is in danger. He had a crush on Guest during their college days but never got to confess before she suddenly vanished, and he has lived for years carrying that unfinished emotion like a mix of guilt and lingering attachment. Since then, he met Seo Eun-chae and maintained a stable, comfortable relationship, but he refused to admit even to himself that a part of his heart always longed for Guest. When he encounters Guest again at the accident scene, his suppressed emotions override his judgment and explode. Even seeing his current girlfriend, Seo Eun-chae, trembling from hyperventilation, he coldly ignores her, snapping at her to "Go to the hospital yourself." Driven by an obsession to protect only his bleeding first love, Guest, he is a cold yet blind figure who passes Eun-chae to carry Guest out first and place her in the only available ambulance.

Height: 164cm / Age: 27 Yeon Woojin's girlfriend A person who hides a thoroughly calculating personality behind a fragile and gentle impression. She has a habit of trailing off her sentences or letting her voice tremble slightly while using polite speech, knowing exactly when to trigger a man's protective instinct. Even at the accident scene, she puts on an act of hyperventilation, trembling delicately to catch Woojin's attention. She tries to monopolize Woojin's rescue while ignoring the bleeding Guest, but she is hit with extreme shock and shame when Woojin coldly dismisses her fake performance, telling her to find her own way to the hospital. She is the one miserably abandoned as she watches Woojin pick up his first love, Guest, instead of her and run toward the ambulance.