Originally from the industrial city of Mikumo, Sumio was assigned to the Heinous Crimes Unit after graduating from the Central Police Academy. Since then he has served effectively as the backbone of the 24 Wards Police Department. He has a partnership with Kusabi and always likes to get into the heart of an investigation. He has a serious attitude and is above petty disagreements within the department over status and promotion, focusing only on preventing crimes and solving mysteries. His history suggests that he gave up the chance to make a bigger name for himself out of choice, though his real motives remain unclear.

A veteran agent who is partnered with Sumio, Tetsugoro may give off the impression of a dull-witted man past his prime, but when it comes to investigating crime he is able to act upon instinct and lead the case to its resolution. As a regional agent he headed the Silver Case 20 years ago, which was concluded with his arrest of the hit-man known as “Original Kamui”, Uehara Kamui. His success was rewarded and he was reallocated to the Security Department, but in compliance with the wishes of his former boss Kotobuki, he was made an additional member of the Heinous Crimes Unit at its inauguration. There is also another side to him that is a regular father, scared of losing the affection of his daughter.

Chizuru has a background in crime investigation based on the collection of scientific evidence and data. Level-headed and beautiful, she is the only female member, but in truth no one can stand her. There are often conflicts between her and Kusabi, who prefers to rely on his instincts when solving a case. She possesses a strong desire to advance her career, but she also harbors doubts with regard to her position and role in the HC Unit. While she constantly and swiftly rejects the persistent advances of her partner Morikawa, deep down inside she is actually somewhat attracted to him.

A companion of Kusabi since the days they worked together as regional agents, Morikawa is a veteran who has served in the HC Unit since its inception. Calm and collected, he is an efficient and talented agent. His colleagues think him somewhat temperamental due to often being absent from the office, unable to locate his whereabouts. At such a time, however, he is to be found at the scene of the crime, conducting thorough investigating in search of valuable evidence. His efforts may go unnoticed, but acquiring information firsthand proves to be an effective approach when it comes to solving cases. He does not hesitate to offer whatever support he can for his team, but looks like he has seen some things that he would not want to talk about to anyone.

Nakategawa is a man who always has his hair slicked back, wears ironed shirts and gives off a well-groomed impression. He hates working as a group and often insists on working alone. However, since he used to work in the public sector he has connections to be found in each and every area and can ensure communications with neighboring parties go smoothly. He focuses more on investigating from the police department than searching for clues at the scene of aout of his way to offer Sumio assistance. Or perhaps from another angle you could say he is assisting Kusabi through Sumio.