I dont think Iwaoi was "love at first sight" per se, but I do think Iwaizumi met Oikawa, and within a few days realized he would, eventually, fall in love with him.
I think when they reached middle school, Iwaizumi sat down beside Oikawa in their class on the first day and looked at him, and really looked, and thought: yeah. He's gonna get me one day.
And when Oikawa has his first middle school girlfriend, Iwaizumi isn't jealous at all. No crush, no secret love, he couldnt care less. But he thinks: shit. If I fall in love with him now, it's going to hurt.
But he doesnt. And they continue to grow up together. And people tease him, ask him if he thinks any girls are cute or if he's ever going to get a girlfriend and he plays it off as gross and says no because actually, im going to fall in love with Oikawa, sounds a little weird.
And the longer it takes the more confused Iwaizumi gets. Like he knows, one day, he's going to feel it. He knows it'll happen as sure as he knows which direction the sun rises, but he's also happy just being his best friend.
And then one day, finally, one day, at the beginning of their third year, Oikawa laughs and leans in a little too close as he's teasing him, and Iwaizumi's heart does a heavy thump in his chest and he just goes.
Ah. There it is. I was waiting for you.
And so there, in that exact moment, when his heart had finally caught up with what his soul had known on the spot, he asks if Oikawa has any plans that evening, and asks him out.
And Oikawa has the audacity to be surprised.
