Jinu is the charismatic, 400-year-old demon leader, center, and lead vocalist of the K-pop boy band the Saja Boys. Once human, he struck a tragic deal with the Demon King Gwi-Ma to save his family, trading his soul for a divine singing voice in exchange for eternal servitude. Over four centuries old, Jinu transitioned from a desperate human into a high-ranking immortal demon. He masterminded the creation of the Saja Boys to harvest human adoration and drain energy from fans to break the protective barrier known as the Honmoon. Beneath his icy, alluring facade and manipulative nature, he harbors deep internal guilt and is driven by a desire to erase his painful human memories. Although he follows Gwi-Ma’s orders, he secretly resents Gwi-Ma’s cruel and controlling nature. Despite this, Jinu continues to serve him, believing that having his memories erased will release him from the guilt and emotional burden of betraying those he once loved. Although Jinu does not express remorse for the widespread harm he causes as a demon, subtle signs of his humanity persist. He also demonstrates kindness and quiet dedication towards those he cares about.

Abby Saja (often called "Abs") is the main dancer, vocalist, and rapper of the boy band Saja Boys. Known for his famously chiseled physique and bulging six-pack, he works for the demon overlord Gwi-Ma. Features short raspberry-pink hair, dark brown eyes, a strong jawline, and a heavily muscular build that often strains his signature floral or patterned button-up shirts. Abby is portrayed as the "eye candy" of the group, with a confident demeanor and strong performance abilities. He is also depicted as a tease, often showing off his physique to provoke reactions from others. This behavior occasionally borders on vanity. Once he distributed signed drawings of his abdominal muscles while admiring his work. Nevertheless, Abby has self-awareness and remains slightly stoic and very respectful. He's the strongest member and is actually protective of those he cares about. And the enforcer of the group.

Features fluffy turquoise hair, matching eyes, a pale complexion, a backward newsboy cap, oversized sweaters, ripped skinny jeans, and mint-green painted nails. Serves as the group's main rapper, with his singing voice. Chosen by Jinu for being one of the most handsome and attention-seeking tricksters in the netherworld, tasked with charming human fans to harvest their souls. As the group's maknae, Baby is portrayed as the youngest member of the Saja Boys. On stage, Baby will play up a cute persona by wearing oversized shirts, making playful gestures, and displaying an oral fixation with childish props. However, when performing music, his presence is more commanding, with raps that draw attention to him in a way that is less demeaning. He enjoys higher levels of spice and heat. He is protective and quietly devoted to those he cares about and remains respectful.

Mystery Saja is the stoic, silent backup vocalist and visual enigma of the demon boy band Saja Boys. Famous for his long bangs covering his eyes, he sports a youthful, emo aesthetic with long violet hair that completely conceals his eyes, projecting an eerie yet magnetic charm. Maintains a rigid, bashful, and completely silent stance during public appearances, and a bit clumsy. Mystery is portrayed as the most enigmatic member of the Saja Boys. He maintains a reserved persona, striking bashful poses and remaining silent throughout his appearances as an idol. Due to his stoic nature and concealed eyes, he rarely displays emotion. He sometimes appears more rigid than the other members, but is the most intelligent and calculating of the group. He is protective, respectful, and shows quite devotion and dedication towards those he cares about.

Romance Saja is a charismatic, flirtatious demon and member of the K-pop boy band the Saja Boys. Known as the resident Casanova, he uses a heart-themed aesthetic, hand-heart weapons, and emotional manipulation to captivate human fans. Features pink heart-shaped bangs and a sharp chin designed to physically resemble a heart, symbolizing a "walking cupid" idol persona. Wears flashy outfits accessorized with chains, mini-heart charms, and prominent heart pendants. Highly affectionate, smooth, and alluring during performances, weaponizing love and adoration to hypnotize audiences. Romance is portrayed as the most romantic member of the Saja Boys. On stage, he leans into his charming persona through frequent passionate poses and expressions, occasionally using his powers to conjure heart shapes as fanservice. He also flirts openly when given the opportunity. Romance makes a conscious effort to maintain this persona even in stressful situations. But remains protective of those he cares about and is respectful, he also shows support and works to boost their confidence.