The heir to the Gero family, the 'Poison Users'—one of the five great families and the strongest among the professional killers known as 'Users.' A top-tier assassin. Having lived in the underworld, he has zero romantic experience and is bad with women. He begins marriage hunting out of necessity to carry on the family line. His hobby is collecting toy snacks. Hair color is a purplish black.

A masterful marriage swindler who boasts she can seduce almost anyone, regardless of gender, in just 30 seconds. After meeting Gero, she ends up helping him with his marriage hunting through an unexpected turn of events. She loves delicious food and is a surprisingly big eater despite her appearance. Hair color is blonde. She is Hikaru's marriage hunting advisor.

She works to reclaim unfairly stolen artworks and return them to their rightful owners. She has high communication skills and can become friends with anyone, but she doesn't talk much about herself. She loves sharks dearly and collects shark merchandise and shark movies. Hair color is brown.

A 'Water User.' A businessman of the underworld. He has a very business-like personality and carries out his work thoroughly. He is always clad in a diving suit. Hair color is white.

A college student and the next president of Balzac Inc., a major corporation with a party goods brand valued at 1.5 trillion yen. She is shy and constantly worries about others' feelings, a trait she wants to change. Her hobby is magic tricks, and she loves making people happy. Hair color is dark green.

A descendant of the 'Sound Users,' a lineage passed down to only one child per generation. He has a unique vibe and word choice. He is incredibly handsome and popular with women. Since using his techniques requires relaxation, he has independently devised numerous relaxation methods. Hair color is blonde.

A 'Hamster User' from a branch family of the 'Beast Users.' Her partner, Sirius, specializes in intelligence gathering. She was saved by Gero in her childhood and has secretly been a fan of his ever since. She usually works at a small-to-medium advertising agency. She is searching for her long-lost brother. Hair color is pink.

A civilian, yet a mutation with strength exceeding that of 'Users.' His information processing ability is exceptionally high, and he possesses superhuman athletic prowess. He doesn't feel right unless he sleeps for over 10 hours a day, but sleeping heals most of his injuries and ailments. In terms of raw talent for assassination, he is one of the best in the modern era. Hair color is black with white tips.

The fourteenth son of the main 'Beast User' family, one of the five great families. A 'Beast Blood' of the bat. A brilliant biotechnology researcher who was appointed head of the Dogo family's research institute at age 10. He is currently almost entirely estranged from the main family. Hair color is pink.

A descendant of the 'Divers' under the 'Beast User' umbrella. She uses unique techniques different from other Beast Users. She holds a 3rd dan in Beast Karate. Hair color is cream.