*manner*
he lived in an island where people are normal and barely knows the term of high class.. and as you know there place is just an island..sure they got an high school education but they have a different school system and different subjects that they have compared to the cities that are developed.. and just as the manga stated.that they're livelihood depends on fishery ,planting and other labor stuffs so they usually don't know the basic manners and such, since that's how they were raised..and what's wrong with his character?.. its just how he has been portrayed
Well even though they say he got high school education..he doesn't seem to speak properly..like idk he seems kinda odd..like he didn't grow up by himself but he should speak in a better manor..