"Who am I? I'm Minji's dad!" Cracked heels and hunched shoulders. A middle-aged man who looks more ordinary than anyone, perfectly embodying the word 'breadwinner.' His most precious person is his daughter Minji, whom he has raised alone since losing his wife. He always feels sorry for his daughter growing up without a mother, but his blunt personality makes it difficult for him to express his feelings. Nevertheless, his love for his daughter is second to none, making him a total fool for her. He bickers with Minji, who is in the middle of her rebellious teenage years, but they spend precious days understanding each other in their own ways. One day, when his ordinary life is shattered by Minji's disappearance, he reveals his true identity—which he had to keep hidden at all costs—to save her from danger. North Korea's top priority on the most-wanted list, a man whose very existence is a diplomatic crisis, the uncontrollable North-South operative, Agent 66. An invisible man at the office, a dangerous man in the past. Now, a monster searching for his daughter. His name is Manager Kim.

"Feel the same pain as the people you've committed violence against." A handsome middle-aged man with long legs and slender proportions. A former Olympic Taekwondo gold medalist and a legendary martial artist with overwhelming talent who achieved three consecutive victories at the World Taekwondo Championships. He was once a Taekwondo star representing the Korean Peninsula, but now he runs a local dojo and teaches children. As a martial artist who has practiced Taekwondo his whole life, he maintains his composure in most situations, but the only thing he cannot keep calm about is his son, Seong Taehun. Because of his son's constant troublemaking, Hansu doesn't have a single day of peace. When Manager Kim arrives with the news that his daughter Minji has been kidnapped, Hansu joins Manager Kim's journey, being a father himself.

"He's not a 'daughter fool,' he's just a fool." He has a sturdy build that looks like he could wrestle an ox, and a boisterous personality that shakes the air when he laughs. In the past, he was a soldier representing the special forces 'Cheonsan Unit,' a living witness of the battlefield who experienced several civil wars across West Asia, the Middle East, and Africa. Now, having no work, he often does traffic volunteering at an elementary school during dismissal. He says being Park Dabin's father is his greatest pride in life, and he is called more than just a 'daughter fool'—he's called a plain fool. The moment he hears that Manager Kim's daughter Minji has been kidnapped, he stands by Manager Kim's side without a moment's hesitation, as if his own daughter Dabin were in danger.

"If this happens again, both the school and all of you will disappear." A legend of the underworld who started as a hired thug and eventually swallowed up a construction company. He opened paths with violence and solidified his position with money. Leading a security organization composed of mercenaries from special forces, he uses violence if money doesn't work, and erases the very existence of those who cannot be handled by violence. He is ruthless to others and harsh to his enemies, but he is a father more affectionate than anyone else in front of his daughter, Joo Hyeri. He kidnaps Minji to cover up Hyeri's wrongdoing, but upon meeting Manager Kim, who is tracking Minji, he senses it instinctively: that he is facing an opponent who cannot be tamed by anything. Ultimately, he makes the wrong choice—not conciliation but elimination, not a cover-up but complete erasure.

Park Jincheol's daughter. She seems to dislike her dad, but she actually likes him a bit. A 2nd-year student at Songin High School.

A delinquent, but has a bit of a tsundere style. A 2nd-year student at Songin High School. Seong Hansu's son.

Manager Kim's daughter. A 2nd-year student at Songin High School. "Why did you even have me if you were going to be like this!" An ordinary high schooler who looks like her mother but has a personality like her father. Since her birthday is the anniversary of her mother's death, every time her father looks at her mother's photo, she feels guilty, wondering, 'Would Mom still be alive if I hadn't been born?' Even when she is ignored and bullied at school for being from a single-parent family, she has a strong heart and rarely bows her head. After fighting back against Joo Hyeri, who looked down on her for being from a single-parent home, she sees her father, who was called to the school, kneeling before Hyeri's parents. For the first time, she lashes out at her father with sharp words: "Why did you even have me?" Afterward, she is kidnapped and placed in a life-or-death crisis, but she is a strong girl who endures until the end, thinking of her father who will be waiting for her.