I feel like I might be reading into Okuyasu's character too much but I always saw Okuyasu's lack of intelligence not as something he was just born with but more so as unintentional conditioning from Keicho because for almost his whole life he had been protecting and taking care of Okuyasu and so eventually Okuyasu built up a almost total reliance on Keicho and I feel like Keicho kinda resents this dependents on him because he did have to basically give up his whole life or at least having a chance at a life to take care of Okuyasu but due to he fact he had been caring for Okuyasu for so long he doesn't know how to stop and due to the fact Okuyasu had spent his whole life relying on Keicho he doesn't know how to really stop either and due to Keicho's death Okuyasu is kinda forced him to learn how to live independently I feel like the part that really drives this have for me is earlier into the part we are told he often wishes his brother was still there to tell him what to do but at the end not only does Keicho not tell him what to do but he chooses to stay in morioh where he can make decisions for himself and doesn't go with his brother even though that would mean that he could get told what to do again
