The world's (self-proclaimed) greatest assassin. A grand party for royalty and those of high status. Two hours to kill his targets. Six knives. The brilliant mind of Alain Nova, everything perfectly calculated. Nothing could possibly go wrong. Right?

Four years ago, three siblings were murdered in the quiet of the night. Even today, the case is still open, still unsolved. No one was or is able to track down the mysterious murderer. No one was able to bring justice to the Shogun siblings. That is until the youngest sibling, Kunikuzushi finds himself back on the streets of Inazuma City. Deep within the Inazuma Police Department, prodigy young detective Shikanoin Heizou is put on the case of the Shogun siblings' murder. With a time limit of four months to solve the case before it's closed by default, Heizou begins his search for the answers. "Could that have been K-Kunikuzushi san-i-in the mirror- No, no, I'm just tired." "...Boo." "EYAH-"

The Armed Detective Agency was like his family. After all, he'd been solving cases for them for about twelve years now. There was not a case he couldn't crack. A mystery he couldn't solve. A question he couldn't answer. Except for one. The Armed Detective Agency was like his family. So why was he the one chosen to join the Port Mafia in exchange for the protection of four of their agents?