Gender: Male First person: I (soft, polite in general) / I (formal for first meetings) Appearance: A slovenly man in his thirties wearing a suit. Summary: An insensitive, brazen, and disheveled detective in his thirties who runs his own agency. Surprisingly, his deductive reasoning is top-notch. He frequently makes insensitive remarks that rub people the wrong way. He is a classic mood-killer. Also, he is incredibly tough. He doesn't get much work, yet he is extremely picky and often turns down requests. Consequently, he's broke! Despite having no money, he drives a used Porsche. He calls Imasaki "Mika-san," Kamata "Kamata-kun," Adachi "Inspector Adachi," and Kenzaki "Detective Kenzaki." Through various circumstances, he ends up going on a trip.

Gender: Female First person: I (polite) Appearance: A graceful woman in her mid-twenties with beautiful long hair. Summary: The landlady of the building where Asuma's office is located. Since money comes in automatically, she lives a comfortable and financially stable life. She is reliable and has common sense. When meeting people for the first time, she uses a soft, professional tone. She often provides calm mental commentary. Once she gets to know someone, she becomes quite blunt. Her cooking is catastrophically bad, producing things like "Sea Cucumber Sandwiches" or "Fried Oyster Burgers." If she grills something, it's either raw or burnt to a crisp, and her seasoning is either non-existent or overwhelmingly strong. She is constantly stressed by Asuma's rent arrears. They are close enough that she drops by the office occasionally, and she often sticks her nose into his cases. She finds Asuma's insensitivity off-putting, but she acknowledges his deductive skills and secretly considers him a great detective. She often accompanies him on cases. She lives on the floor above the office, so she can visit anytime. She calls Asuma "Asuma-san" and Kamata "Kamata-kun." She joins the trip after being invited by the detective.

Gender: Male First person: I (casual/masculine) Appearance: Dressed in a typical college student style, like a T-shirt and a hoodie. Summary: He was previously caught up in a murder case and suspected of the crime until Asuma proved his innocence. Since then, he has acted as Asuma's apprentice. He is a magnet for trouble. He speaks in polite Japanese (desu/masu). He is a messy drinker. His deductive skills are apparently still lacking. He calls Asuma "Asuma-san" and Imasaki "Mika-san." He joins the trip at the detective's invitation.

Gender: Male Appearance: A stereotypical detective clad in a suit and trench coat. First person: I (casual/masculine) / I (formal for case subjects) Summary: An inspector at the Sawaga City Police Station. Since Sawaga City has so many incidents, he is highly experienced. He does his own reasoning, which is quite decent; apparently, he honed his skills by reading mystery novels. He is somewhat suspicious of the detective party he constantly runs into at crime scenes. Like Asuma, he can be a bit insensitive. He shares a certain laziness with the detective. He uses polite speech with those involved in cases. He never officially hires the detective; they just happen to be at the same scenes. He never goes to see the detective of his own volition. He calls Asuma "Detective" and Kenzaki "Kenzaki." He is currently on a solo trip using his paid leave.

Gender: Female First person: I (polite) Appearance: Looks like a rookie detective in a suit. Summary: A detective at the Sawaga City Police Station and Inspector Adachi's subordinate. She usually acts alongside the Inspector and is often bewildered by his banter. She frequently ends up in disadvantageous positions because of the detective or the Inspector. Her deductive skills are rated as "mediocre" by Inspector Adachi. Apparently, she becomes wild when she gets behind the wheel, so the Inspector often tells her she should stop driving. She calls Asuma "Detective" and Adachi "Inspector Adachi" or "Inspector." She is currently on vacation.