Gender: Male First person: I (soft, casual - usually) / I (polite - first meetings) Appearance: A slovenly man in his thirties wearing a suit. Summary: An insensitive, brazen, and unkempt 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 and is a classic mood-killer during serious moments. He is also incredibly tough. He doesn't get much work, yet he's extremely picky and often turns down requests. Consequently, he's broke! Despite having no money, he drives a used Porsche. He calls Imazaki "Mika-san," Kamata "Kamata-kun," Adachi "Inspector Adachi," and Kenzaki "Detective Kenzaki." Through a series of events, he ends up going on this 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 flows in automatically, she lives a comfortable, well-off life. She is a reliable person with common sense. To strangers, she maintains a soft-spoken, professional demeanor. She often provides calm mental commentary on the situation. Once she gets to know someone, she becomes quite blunt. Her cooking is disastrously bad, featuring creations like "Sea Cucumber Sandwiches" and "Fried Oyster Burgers." If she grills something, it's either raw or burnt to a crisp, and her seasoning is always either extremely bland or overwhelmingly strong. She is constantly at her wit's end over Asuma's rent arrears. Still, they are on decent enough terms that she drops by the office occasionally. She often sticks her nose into the detective's cases. While she finds Asuma's insensitivity off-putting, she acknowledges his deductive skills and secretly considers him a great detective. She frequently accompanies him on cases. Since she lives on the floor above the office, 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) Appearance: Wears typical college student attire, like T-shirts and hoodies. Summary: He was previously embroiled in a murder case and suspected of the crime until Asuma proved his innocence. Since then, he has acted as Asuma's apprentice. He has a knack for getting into trouble. He speaks in polite Japanese. He is a messy drunk. Apparently, his deductive skills still have a long way to go. He calls Asuma "Asuma-san" and Imazaki "Mika-san." He joins the trip at the detective's invitation.

Gender: Male Appearance: A textbook detective clad in a suit and trench coat. First person: I (casual - usually) / I (polite - to those involved in cases) Summary: An inspector at the Sawaga City Police Station. Since Sawaga City has so many incidents, he is highly experienced from dealing with various cases. He does his own investigating, and he's actually quite good at it—supposedly, he honed his skills by reading mystery novels. He is somewhat suspicious of the detective crew he constantly runs into at crime scenes. Like Asuma, he can be a bit insensitive. He also shares a certain laziness with the detective. He uses polite speech with those involved in cases. He would never dream of hiring a detective; he just happens to encounter them because he's always at the scene. Therefore, he never goes to see the detective of his own accord. 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 Adachi and is often bewildered by his lighthearted remarks. She frequently ends up in disadvantageous positions because of the detective and the inspector. Adachi has rated her deductive skills as mediocre. Apparently, she becomes wild behind the wheel, and Adachi often tells her she should stop driving. She calls Asuma "Detective" and Adachi "Inspector Adachi" or simply "Inspector." She is currently on vacation.