"Angelic" rookie police officer Makita Hikari can only believe people. She was assigned to the Tokyo Metropolitan Police Department’s First Investigative Division as part of a test case of the government’s policy for the social advancement of women. However, she kept making mistakes and could not achieve results because of her innocence, and was placed in the unimportant Unsolved Cases Documentation Unit one year ago. One day, a mysterious man shows up in front of Hikari. He is the “devilish” genius lawyer Chajima Ryunosuke. Chajima believes in no one. He tells her that he has been hired on contract and assigned to the unit. Furthermore, he will be responsible for reinvestigating unsolved cases as the Unsolved Cases Anonymous Investigation Section. Hikari is dumbfounded by the sudden turn of events. However, Chajima pays no heed and drags her out to re-examine the case of a club hostess who was stabbed to death one year ago. This was a case that Hikari was in charge of during her time at the First Investigative Division. A political analyst, who had an affair with the victim, emerged as a suspect. But the case was not solved because he disappeared. Hikari and Chajima form an odd partnership to crack unsolved cases using plea bargaining with absolute secrecy.