Eun Chae-ni is a bright, chaotic, and hot-tempered 27-year-old known as her hometown's resident "trainwreck". Born with a severe congenital heart condition and fiercely shielded by her grandmother, she grew up unable to leave her small city, fueling a desperate dream to travel the world. After a botched fake-kidnapping scheme meant to secure travel funds goes catastrophically wrong, she is exposed to toxic waste, experiences a brief death, wakes up with a modified "superheart" that grants her the power to teleport whenever her heart rate spikes.

Lee Un-jeong is a rigid, socially awkward civil servant who hides a powerful, trauma-induced telekinetic ability behind his straight-laced persona. As a surviving test subject from brutal childhood experiments, he attempts to suppress his powers to live quietly while secretly tracking his past. However, his highly structured life is completely upended when he is forced to investigate local disappearances alongside a chaotic, teleporting woman and her clumsy neighborhood friends.

Son Gyeong-hun is a kind-hearted, middle-aged neighborhood man who runs a local key-cutting shop. After being exposed to chemical waste, he gains the unusual ability to stick to walls, ceilings, and objects at will. His adhesive powers become surprisingly useful for stealth and espionage as he joins his clumsy neighbors in protecting the city. However, there’s one awkward flaw: his powers activate involuntarily whenever he lies or says something untrue.

Kang Ro-bin is a timid, pure-hearted gentle giant who is known as his hometown’s biggest pushover. He works peeling onions at a local restaurant and is fiercely loyal to his only true friend, despite her chaotic personality. After being exposed to chemical waste, he develops incredible Hulk-like strength that is triggered by strong emotions. When he feels hurt, insulted, or hears profanity, his powers activate, causing him to tear through walls while crying or fighting in an unexpectedly dramatic way.

Dr. Ha Won-do is a ruthless mad scientist obsessed with achieving immortality through brutal biological experimentation on orphaned children. After serving 20 years in prison for his horrific lab crimes, he returns as the leader of a cult-like organization to reclaim his surviving superpowered test subjects. His ultimate plan involves tracking down a rare, regenerating "eternal heart" mistakenly transplanted into a local woman and unleashing a hazardous pollutant to trigger widespread genetic mutations.

Kim Pal-ho is a powerful and deeply traumatized member of the superpowered trio who sees a ruthless mad scientist as his father figure. After surviving brutal childhood genetic experiments, he gained the ability to manipulate gravity, creating powerful force fields and overwhelming crushing force. He serves as a loyal enforcer for a doomsday cult, carrying out dangerous abductions without hesitation. However, using his powers too much causes his body to painfully harden like stone, eventually leaving him vulnerable and exhausted.

Seok Ju-ran is a fiercely loyal and dangerous member of the superpowered trio who considers a ruthless mad scientist her father figure. After surviving brutal childhood biological experiments, she gained powerful telepathic abilities, allowing her to read memories, manipulate minds, and control people through touch. She becomes a feared enforcer for a doomsday cult, relentlessly pursuing those connected to the rare regenerating heart. Yet absorbing the emotions and trauma of others takes a heavy toll on her mind, making her vulnerable despite her strength. She is also deaf and relies heavily on her other senses.

Seokk Ho-ran is a cold-natured member of a superpowered trio who sees a ruthless mad scientist as her father figure. After surviving brutal childhood genetic experiments, she gained the ability to project hallucinations and distort reality, forcing people to experience their worst nightmares. The experiments severely deformed her left eye, leading her to wear dark sunglasses. Despite her trauma and complicated feelings for a childhood love, she fiercely protects her found family.

Gu Jun-mo is a calm, quiet, and mysterious private investigator hiding a painful past. A survivor of brutal childhood biological experiments, he escaped the facility and built a seemingly normal life under the protection of his strict, restaurant-owning grandmother. Despite wanting peace, his investigative skills lead him to uncover dangerous clues and threats. When his traumatic past resurfaces, he can shift from a dependable ally into someone cold and unpredictable.

Kim Jeon-bok is a strict, charismatic, and protective grandmother who runs a well-known restaurant in Haeseong. She is Chae-ni’s only remaining family and deeply cares for her, often showing her love through a tough and commanding attitude. Beneath her glamorous and confident exterior lies a mysterious, darker past that she keeps hidden. Despite her secrets, Jeon-bok will do anything to protect her granddaughter and the people she considers family.