Jean Otus isn't that smart
ACCA 13 Territory Inspection Dept was supposed to be an anime about a genius inspector uncovering a Coup d'état. The problem is, Jean (the main character) really isn't that smart.
We got a glimpse of Jean's intelligence in the first episode, but then we didn't get to see it again...anywhere. It made it seem like his brilliance was just a fluke. You know, maybe he got lucky.
In the first episode, Jean is sent out to do some investigatory work at one of ACCA's branches where he stumbles upon some irregular data. The data seems normal to everyone else, but Jean seems to have a knack for seeing what others do not — except when it comes to himself.
Jean is clueless about his own life.
Jean and his sister are royalty but never knew it. They inherited an apartment from their princess mother, but Jean never questioned how they obtained it. He never traced his genealogy and learned he's related to the king; he never realized an old man (Nino) had been guarding him his whole life. Yet, he's an inspector!
The dumbest mistake Jean made was at the end of the anime when he supported the worst leader for the nation. It came after Jean realized the purpose of the Coup d'état was to put Jean himself on the throne.
Everyone knew it but him.