Nakano Hitomi is an ordinary employee who works for the Metropolitan Police Department’s General Affairs Section. Her job is to check the receipts for investigation expenses that the detectives pay in advance, but she is extremely sharp in detecting cases because she was raised by her father, who is a swindler.

When serial killings and injuries occur, she is also the first to realise that the victims' names are linked to a word game in which one victim’s name contains the last character of the name of the previous victim. Hitomi uses detective Togawa of the First Investigative Division, whom she became acquainted with after finding discrepancies in his receipts and scheming lawyer Shirai Shinnosuke who works his way into the favour of victims to find work that pays well, to get close to the truth of the case.