Kidow is the main protagonist of the series and a seventeen-year-old exterminator living in the post-apocalyptic world. His home is Trade City E-05 in Southwest Asia, a region on the borders of the Extreme East, where he has built a reputation for being extremely efficient at his dangerous job of killing Cagasters, humans who have been transformed into giant insect monsters by a mysterious virus. Before the events of the story, Kidow was orphaned and taken in by a man named Lazarus, who became his adoptive father. It was Lazarus who taught Kidow the harsh lessons of survival in the Cagaster-infested Far East, shaping him into the hardened warrior he becomes.

Kidow presents himself as a cold, disciplined, and extremely guarded individual with a poor attitude. He has trouble handling things that remind him of his own youth and behaves as though he has no empathy, but this is a defense mechanism; he actively resists feeling empathy to protect himself from the pain of loss in a world where death can come at any moment. He believes one should never hesitate to kill a Cagaster, even if the infected person still appears human, a principle drilled into him from a young age. Despite his attempts to appear detached and motivated solely by money, he still finds himself wanting to protect others, revealing a more conflicted and compassionate side that slowly emerges through his interactions.

His primary motivation at the start of the series is survival and earning money through his work as an exterminator. This changes when he encounters a young girl named Ilie. After saving her from a Cagaster attack, Kidow reluctantly agrees to a dying man's request to escort Ilie to her mother, a promise that becomes the central driver of his journey. As he travels with Ilie, his role evolves from a mercenary protector to a genuine companion, and he begins to question the rigid morality of exterminating the infected without hesitation. He faces a significant challenge when he loses his memory after being struck in the head during a mission, forcing Ilie to care for him. As he slowly regains his memories and learns more about the horrors of the Cagaster virus, his determination to protect her and help her find her mother only strengthens.

Kidow's most important relationship is with Ilie. Her innocent and compassionate attitude toward the infected directly contrasts with his brutal worldview, and it is through her that he begins to grow emotionally. He is often seen working with a scavenger partner named Jin. His past is deeply tied to his adoptive father, Lazarus, who taught him how to survive, and he also had a brief, unrequited crush on a woman named Rexia, whom he let go when he realized she did not love him back. His primary antagonist is Acht, with whom he has a final, decisive confrontation.

Kidow undergoes significant character development throughout the series. He starts as an emotionally stunted young man who does not know how to interact with others or understand boundaries but gradually learns to forge a real connection with Ilie. Their dynamic feels natural as they find a middle ground, with Kidow's emotional growth being a central focus of the narrative. His journey forces him to confront his own past and the rigid code of conduct he was taught, ultimately redefining what it means to be human in a world overrun by monsters. It is also revealed that Kidow's real name is Ileck.

As an exterminator, Kidow is a highly skilled warrior with notable combat abilities. He is proficient with firearms, using a gun that his fit and bulky physique allows him to wield without any recoil, and he also employs blades and tactical movement to take down massive insect threats. He possesses specific knowledge of the Cagasters' biology, knowing that while bullets and blades have little effect on most of their bodies, they have a weak spot, which is typically located behind their neck.