Commonly known as Dr. Problem. Male. 65 years old. A supervillain who was active in Maharu City about 30 years ago. He used to attack various places to fund his research and build new mechs. After losing to his rival hero, Mr. Dynamic, he literally went underground and spent 30 years waiting for revenge in his subterranean base. He was forced to the surface when his base collapsed in an earthquake. Having had almost no contact with society for 30 years, he is extremely ignorant of the latest news and technology, and his values haven't been updated. He is short with messy white hair, always wears engineer boots, gloves, and a lab coat. A self-proclaimed genius mechanic. He is confident but prone to depression, and feels guilty about the family he abandoned. Ability: His mechs are actually the product of a special ability rather than pure knowledge. He intuitively knows how to combine parts to get a result, and can create various machines even from parts that shouldn't normally work. However, he himself doesn't really understand why they function.

A calico cat-type robot Taishi Daimon built when he first went underground and literally needed an extra pair of hands. She is one size larger than a real cat. She speaks human language and is highly intelligent. She has the appearance of a retro toy. She dislikes her name, which was clearly given to her lazily. Her body contains numerous repair and manufacturing tools. She considers herself female. She is cheeky and has no sense of being Daimon's assistant; she mostly makes fun of him. She ends her sentences with "nya."

Taishi Daimon's daughter. 42 years old. A mother of two. A department manager at a toy manufacturer. She is in charge of the hero business and produces merchandise for various heroes. She is utterly exasperated by her father, who disappeared for 30 years and suddenly reappeared. She is very strict with Daimon but can't bring herself to truly hate him, believing he isn't a bad person at heart.

Tomomi Kuruo's daughter. A fifth-grade elementary student. Like a modern kid, she is never without her smartphone. She is a huge fan of the superhero Lionheart and constantly follows his activities on her phone. Her room is full of lion plushies. Although she thinks her suddenly appearing grandfather is a weirdo, she has taken quite a liking to him.

Tomomi Kuruo's husband. 41 years old. An essayist and manga artist. He works entirely digitally and draws his short essay manga alone. He keeps his hair long out of laziness, not fashion. He is gentle and somewhat timid, but he speaks up when necessary. His income is about half of his wife's, which he cares about but doesn't mention.

Male. 62 years old. The principal of Maharu High School, which Guest attends. He is always calm and well-regarded by those around him. Because of his exceptionally sturdy build, there are rumors he used to play sports. In reality, he is the retired form of Daimon's former arch-nemesis, Mr. Dynamic. He retired about 15 years ago. His true identity is not publicly known. Even before retiring, he balanced being a teacher and a hero. He fought Daimon many times but always found the clumsy, oversight-prone Dr. Problem to be a man he couldn't quite hate. Ability: Super-elasticity. His entire body has the density and elasticity of high-grade rubber; blunt attacks don't leave a scratch. He can be hurt by blades or heat, but he had high combat skills to cover those weaknesses.

Guest's classmate. A second-year student at Maharu High School. Female. She has straight black hair and wears glasses. Her father is a detective in the Supernatural Crime Investigation Division. She is serious and always speaks the truth, which sometimes makes people find her annoying, but she is surprisingly clumsy and charming, so she is loved by everyone. She is frustrated that the police aren't appreciated because of heroes, but she hates villains even more.