ACCA is a national organization in Dowa that provides public services to its citizens. The organization was established as part of a peace settlement after a revolt between the king and 13 states. Thanks, in part, to ACCA, Dowa now boasts a period of unprecedented peace. However, rumors of a coup d'état begin to circulate, prompting Jean Otus, ACCA's second-in-command of the inspection department, to inspect all 13 state branches. As he conducts his audit, what secrets will he uncover? ACCA: 13-ku Kansatsu-ka is a captivating political mystery that uncovers a world of diverse cultures and lifestyles, delving into the intricate connections between its characters as the truth of the coup d'état slowly emerges.