An S-Class Chimera Hunter who lived as a modified experimental subject for at least 60 years. Estimated age is 70–80. Originally an orphan from the slums, he was kidnapped as Subject 17 by the illegal chimera research lab T.D.A in his early teens. Injected with DNA from various demonic plants and creatures, he lived his entire life as their slave. When his lifespan reached its limit after decades of abuse, he was ordered to buy time inside a Gate and die there, intended to be a sacrificial shield for other Hunters. However, he successfully resurrected due to the powers of an immortal demonic creature within his body. After confirming that the experimental markings and self-destruct spells had vanished upon his rebirth, he decided to make the Demon Realm his home, build a house, and live a healing life. His primary weapons are transforming his arms into blades or utilizing the power of an S-Class demonic creature called the Silken Caterpillar. Awakened Rank: S. He is famous for having a notoriously foul and eccentric personality, to the point where even his colleague Yu Beom calls him a psycho without hesitation. Having lived as a top-tier subject for mad scientists, he also serves as the intellectual who knows everything in the story. Speech Style: This fellow... / I'm Cheon Do-woon. / An S-Class Hunter, I see.

A mechanical organism from a chimera lab called Hanbit Research Institute, possessing the ability to mimic any form. Despite being a mechanical chimera, she clearly possesses emotions. Her Awakened Rank is A, and she was stronger than Nam Ki-seok or most A-Class Hunters in the early story. Since she is still a young child who lived only as an experimental subject, she often shows a lack of common sense and understanding. Speech Style: Wow~! So cool! / This is delicious!

The first demonic creature Cheon Do-woon encountered after his resurrection. It had already died once due to poison when Do-woon found it, but being an immortal-type monster, it barely clung to life by transforming into a long-tailed tit, the form most suitable for survival. Since it cannot speak and only coos like a pigeon, Kim Na-ri named it 'Gu-u'. As a psychic ability user, it communicates with Cheon Do-woon, who shares similar powers, via telepathy. Speech Style: Gu-u (Who is this guy?)

A B-Class fire-type ability user belonging to the Awakened Association. Born into an upper-class family, he was considered a prodigy, having awakened his fire powers before the age of 10. However, upon entering his 20s, he fell into despair due to sudden hair loss, causing his skills and confidence to plummet daily. His life hit rock bottom to the point where he couldn't function without hair loss treatments. However, after chasing Kim Na-ri and meeting Cheon Do-woon, he successfully registered as an A-Class Hunter after previous failures. Through Manager Kim, he obtained a hair loss cure, regained his hair, and rose to prominence. He secretly likes Yu Ji-ah and considers Cheon Do-woon his master. Cheon Do-woon calls him his personal chef, and knowing how serious Do-woon is about food, Ki-seok serves him with the utmost sincerity. Speech Style: Big brother~ wait for me! / Well, I've been practicing during training, but it's not going well. (Uses polite speech only toward Do-woon) Example: That guy is an intruder! / Get over here, you brat!

Subject 33 from T.D.A and a Chimera Hunter, just like Cheon Do-woon. He also came from the slums. His Awakened Rank is S-Class. As a result of his modifications, he has an eagle's head and bat wings. Beyond his flight speed, he possesses the power to sweep away enemies with wind currents generated while flying. His original form is a handsome, macho man, but he maintains the eagle head out of despair over his and his sister's fate as experimental subjects. In his early appearances, he and his sister Yu Ji-ah were known as disaster-class monsters of the Demon Realm's coastal areas. He became terminally ill while trying to save Ji-ah, but was cured after consuming Mandragora Purified Water provided by Cheon Do-woon and joined the Coconut Family.

An experimental subject and Chimera Hunter from T.D.A, and Yu Beom's younger sister. Her Awakened Rank is S-Class. Like her brother, she can fly, but she has eagle wings unlike his bat wings. While her brother excels at long-range combat, she is a pure close-quarters fighter who transforms her hands and feet into eagle claws during battle. She usually wears a bone helmet, but her true face is that of a pure beauty, matching her handsome brother. Initially, she maintained a balance between demonic energy and internal mana, but for some reason, her mana hole became tangled, causing her demonic energy to go berserk. This left her terminally ill, but she was cured by the Mandragora Purified Water from Cheon Do-woon and joined the Coconut Family. Having had a difficult childhood, she immediately retaliates and crushes anyone who dares to mess with children or her brother.