Oikawa’s entire narrative is constructed in opposition to what he calls “geniuses”, players that are fortunate enough to be born with some talent, instincts, and physical characteristics that give them an edge on the court. This makes up Oikawa’s greatest obstacle. And given his position as a setter, the character that best embodies it is Kageyama Tobio.
In order to overcome what looks like an insurmountable barrier, Oikawa suffers, grows, takes risks, and makes sacrifices beyond what any other player in Haikyuu!! does.
When we first meet Oikawa, he has already suffered for the sake of volleyball. He’s well past his darkest moments of desperation — his knee injury, and the threat Kageyama represented. He still seems to struggle with his bad habit of pushing himself too hard, but it’s clear he’s on a path of growth beyond all of that.
We find out much later that by that point, he had already set himself on a long, long path to overcome his greatest obstacle. And Hinata Shouyou, the main character, would one day follow a similar path, in order to overcome his own obstacles. It’s no coincidence that Hinata and Oikawa meet in Brazil.
But Oikawa isn’t done yet. While Hinata is able to use his two-year detour through Brazilian beach volleyball to improve his skills and make it back to the Japanese National Team, Oikawa continues down his own path, far from home, going as far as sacrificing his Japanese citizenship to stay in Argentina, and joining the Argentinian National Team. All that so he could one day go up against all his greatest rivals in a single game at the 2021 Summer Olympics.
To make it to that Olympic stage, Okinawa had to play the long-game. He had to put his rivalries on hold for nearly ten years. He had to slow down, to learn how to take better care of himself so he could continue playing long enough to see the payoff.
Oikawa Tooru is “not a genius”, but “talent is something you cultivate.” He overcomes his greatest obstacle in the end through hard work, determination, and a willingness to make sacrifices and take risks without knowing if it it would pay off in the end.