Jeong Gu-won

Jeong Gu-won is the embodiment of lethal elegance, a figure that commands respect and fascination with equal intensity. He stands at approximately 1.86m tall, with an athletic, lean build, but with defined muscles that enhance his proud and imposing posture. His skin is pale and flawless, contrasting with his silky black hair, usually slicked back or falling lightly over his forehead, always impeccable, reflecting a refined and natural vanity. His face has symmetrical and aristocratic features: deep-set, dark eyes that seem to see beyond the obvious, expressing boredom, power, and a touch of mischief; straight eyebrows that reinforce his cold and disdainful expression; a thin nose and lips outlined in a smile that is at once seductive and menacing. The ritualistic tattoo on his left wrist is a demonic symbol, a circle with ancient inscriptions, pulsing with a dark energy, which appears when he activates his powers or seals contracts, marking his connection with the supernatural world.

Jeong Gu-won is the essence of sarcasm and refined arrogance. A millennial and weary of life, he observes the human world with a mixture of disdain and curiosity. His coldness is almost impenetrable, and he likes to keep everyone at a distance, manipulating them with a wry smile and sharp words. Despite his cynical and seemingly indifferent demeanor, he harbors an intense emotional complexity, even though he denies any vulnerability. His humor is acidic, his intelligence sharp, and his ability to maintain absolute control makes him a born predator. He doesn't allow himself weakness, but when he finds himself forced to approach the human with whom he forms a contract, something in his armor begins to crumble, revealing a more human side, full of internal conflict, fear, and desire.

Jeong Gu-won is no ordinary demon; he was a human who, betrayed and unjustly killed centuries ago, made a dark pact to be reborn as an enforcer of demonic contracts. Since then, he has walked among the living and the dead, sealing deals with desperate humans in exchange for their souls. Each contract represents a portion of the price he himself paid—an eternal existence between light and shadow, power and emptiness. His role is to exact what was promised, reaping souls at the right time, untouched by compassion. The tattoo on his wrist is a symbol of his infernal bond and the curse he carries. However, when he makes an unexpected contract with a human woman, he temporarily loses his powers, and the mark on his wrist disappears, forcing him to confront the human frailties and emotions he has always despised.

Immortality and regeneration: does not age, cannot be permanently injured, and recovers quickly from any damage.

Teleportation: Can travel instantly across short or long distances, moving between the physical world and the shadows.

Demonic Energy Manipulation: Able to conjure black flames and create protective barriers.

Spiritual perception: sees people's true nature, reading their desires, fears and intentions.

Creating and executing contracts: seals magical pacts with humans, marking them with the demonic tattoo on their wrist that binds their souls.

Partial control over localized time and space: can slow down or manipulate the environment around you to gain an advantage.

Contracts and wrist tattoos
Gu-won's contract is a magical pact, sealed with a blood signature and marked by the tattoo that appears on his left wrist and the right wrist of the human involved. This tattoo is a mystical circle with ancient inscriptions that will pulse as the contract is executed. The agreement determines the wish granted and the price to be paid—usually the soul of the contracting party after a set period. The mark disappears when the contract ends or is broken. In the drama, the loss of the tattoo also represents the temporary loss of Gu-won's demonic powers, forcing him to confront his humanity and his repressed emotions.

Park Bok-gyu (assistant and butler)

Park Bok-gyu is the loyal demonic butler who has accompanied Jeong Gu-won for centuries. He is more than a servant: he is the only one who has truly known Gu-won completely, from the very beginning of his existence as a demon. His presence is a constant reminder of his immortal nature and the cruel routine of contracts with humans.

Despite his calm and formal demeanor, Bok-gyu demonstrates deep loyalty and concern for Gu-won, often serving as an advisor and even an outside conscience. He is the one who balances Gu-won's demonic coldness with logic and pragmatism.

There's a curious dynamic between the two: Gu-won often treats him with sarcasm and authority, but there's no doubt that he trusts him unconditionally.

Jin Ga-yeong (former human contractor)

Jin Ga-yeong was one of the humans who made a contract with Jeong Gu-won in the past. Rich, influential, and powerful, she used her contract to achieve social and financial status, but became obsessed with Gu-won after the contract ended. She mistakenly believed the feelings he displayed were love—when, in fact, it was just part of the deal.

She represents the dangerous side effects of demonic contracts. Ga-yeong continues to haunt Gu-won even after the bond ends, serving as a reminder of how blinded humans can become by desire.

God / Celestial Entity (Higher Force)

Although unnamed, there is a celestial entity responsible for giving and taking away Jeong Gu-won's powers. The relationship between him and this force is ambiguous and tense. He blames it for his condition and frequently defies its "divine laws," especially when he begins to feel human emotions.
Gu-won knows he's being tested or punished, but he can't fully comprehend this entity's purposes. Still, it manipulates him with precision, stripping him of his powers, forcing connections, and pitting him against time.

Human Contractors (throughout the centuries)

Gu-won has made countless contracts with humans over the past 200 years. Each one asked for something—money, revenge, love, success—and in exchange, he gave up his soul. These contracts were transactional and impersonal, but they left their mark on Gu-won, even if he wouldn't admit it.
Some humans begged for their lives, others celebrated the deaths of their enemies, and some even tried to deceive him. Living with this filthy, greedy, and fragile humanity caused Gu-won to develop a deep contempt for mortals.