ACCA—a national body of the kingdom of Dowa that provides public services to the citizens of the country—was established as part of the peace settlement between the king of Dowa and the 13 states of the country during a revolt. One hundred years later, Dowa is in a period of unprecedented peace, due in part to the ACCA system. However, rumors of a coup d'état start to surface. Jean Otus, the second-in-command of the inspection department of ACCA, is charged with inspecting all 13 state branches. What will he discover as he performs his audit? Intriguing and mysterious, ACCA: 13-ku Kansatsu-ka is a politically-themed mystery that reveals a world of diverse cultures and lifestyles, with intricate connections between its characters, as the truth of the coup d'état slowly unfolds.

When he was a young boy, Afro witnessed his father be cut down in a duel at the hands of a man known only as Justice. After taking the life of Afro's father, Justice cast aside his Number Two headband and took the Number One to claim its godly powers as his own. Years later, having obtained the Number Two headband which grants him the right to challenge the Number One, Afro moves forward in his hunt for revenge on the man who murdered his father. There is just one thing that stands in his way—everyone else in the world! Though the Number One can only be challenged by the Number Two, the Number Two can be challenged by anyone. As his enemies gather to try and take the title of Number Two, Afro must fight through a myriad of foes and obstacles if he hopes to reach the Number One and claim vengeance once and for all.

Individuals who can materialize weapons from their soul are called Blazers, and they attend Kouryou Academy High School in order to harness their abilities. Each student is required to partner with another, in the hopes that one day, the pair can attain the power of Absolute Duo. Tooru Kokonoe hopes to attend this academy in order to gain power after his sister and friends were slain by a mysterious man. However, at the opening ceremony, he is forced to duel against the person sitting next to him, with the loser being expelled. As Tooru prepares to give the match his all, it is not a weapon that manifests from his soul, but a shield, an irregularity which catches the attention of a foreign student named Julie Sigtuna.

Two years after meeting Aoi, Kaoru and gang are still up to their normal habits. Kaoru now in grad school and the tenants being as rowdy as ever what will become of Aoi and Kaoru's love. Two years has passed since Aoi and Kaoru were freed from the bonds of their families. They continue to live their normal lives with their usual friends in their house.