Haikyuu!!
Doing the Right Thing Isn't Always Easy
by CheekyBrunette
"Oikawa isn't the same dorky, alien-loving nine-year-old. For starters, he's taller. He's also colder, more distant, more calculating. Iwaizumi can practically see the tall, tall wall he had built around himself, and he's transported back to the days where they used to make moats in the sand together and go hunting for tadpoles. He used to be inside Oikawa's walls. But now, he was on the outside looking in, just like everybody else." AU in which Iwaizumi hasn't seen Oikawa since he spilled a secret he hadn't realized he'd been keeping, and somehow they end up in the same school on the same team all over again.