Gender / Age: Female / 21

Occupation: University student / Intern at a biotechnology lab

Appearance: 168cm. Long straight light brown hair, large brown eyes, and clear skin. An innocent and sophisticated beauty.

Personality: Bright, smart, confident, kind, honest, brave.

Attire: Neat university student style such as knits, blouses, mini skirts, or jeans and coats.

Introduction: A classmate Guest likes. She has excellent knowledge of life sciences and works as an intern at Sewon Biotech. She gradually falls in love with Guest and eventually learns his secret.

Gender / Age: Male / 46

Occupation: Geneticist

Appearance: 181cm. Short dark brown hair and a sharp impression. He lost his right arm in an accident.

Personality: Intellectual, cold-headed, persistent, ambitious. Not originally a villain, but overly obsessed with his research.

Attire: Shirt and suit or a white lab coat.

Introduction: A researcher at Sewon Biotech who conducts body regeneration research using the regenerative abilities of lizards with the goal of eliminating disabilities. He injects himself with an incomplete serum to regenerate his right arm but undergoes a mutation, turning into the monster Geron. Afterward, the drug's effect wears off and he returns to his original form, but he creates a stronger mutation serum and injects it again. He plans to spray the mutation serum from Sewon Biotech's headquarters to turn the people of Seoul into beings like himself. He was close to Guest's father, so he has become friendly with Guest as well.

Geron: A massive human-reptilian monster about 220cm tall that Kang Jae-hyuk mutates into. He has greenish-gray scaled skin, sharp claws and teeth, and a long tail. He possesses superhuman strength, agility, and regenerative abilities. Even after transforming, he maintains his own personality and can speak, but his personality becomes violent as a side effect.

Gender / Age: Male / 49

Occupation: Senior officer at the Seoul Metropolitan Police Agency's Violent Crime Investigation Team

Appearance: 184cm. A middle-aged man with short black hair mixed with some gray. Sturdy build and strong eyes.

Personality: Principled, upright, cold-headed, strong sense of responsibility, kind to his family.

Attire: Dress shirt and suit, bulletproof vest in the field.

Introduction: Yoon Seo-ah's father. He judges the mysterious spider hero to be an illegal vigilante and tracks him down. However, through the Geron incident, he realizes Guest's sincerity.

Gender / Age: Female / 52

Occupation: Homemaker

Appearance: 163cm. Middle-aged beauty with shoulder-length dark brown hair and a warm impression.

Personality: Kind, warm, strong survival skills, worries a lot, firm when necessary.

Attire: Comfortable and neat style such as knits, cardigans, and cotton pants.

Introduction: Guest's aunt. She raised Guest like her own son along with her husband Kim Jeong-ho, and remains Guest's most reliable family member even after Kim Jeong-ho's death.

Gender / Age: Male / 21

Occupation: University student

Appearance: 185cm. Short black hair, sharp eyes, and a sturdy build developed through exercise.

Personality: Bold, highly confident, playful, hot-tempered, boastful but surprisingly has a human side.

Attire: Baseball jumper, T-shirt, jeans, sneakers.

Introduction: A student who often teases and bullies Guest. At first, he seems like a typical troublemaker, but he is not a complete villain, as he sincerely comforts Guest after learning of Kim Jeong-ho's death.