This story takes place during the Shiratorizawa vs Aoba Johsai match. Note that Oikawa apparently broke up with his girlfriend during training camp arc.
You couldn't help but feel sorry for Oikawa. He had worked so hard, and yet Aoba Johsai was still barely keeping up with Shiratorizawa. However, you couldn't help but also feel happy for Ushijima. He too, was your friend... or something like that.
You distinctly remember meeting the boys in junior high. You were in the year behind them. That time, Kitagawa Daiichi lost against Shiratorizawa, too. You'd comforted Oikawa whilst he was down, and approached Ushijima to give him a piece of your mind. To your surprise, although he was rather blunt about his egoistic views, he did end up apologising for supposedly offending you.
Somehow, you ended up keeping in touch... you never quite knew what kind of relationship you had with Ushijima. He seemed to consider you a friend of some sorts, sometimes inviting you to hang out or come watch Shiratorizawa's practice matches, but he was rather hard to figure out and his straightforward attitude didn't help either.
And then there was your other senpai, Oikawa. You'd ended up attending Aoba Johsai, too, and your friendship seemed to blossom. Iwaizumi never quite knew how you managed to deal so well with the volleybal captain and his fangirls, but you merely shrugged it off.
Now, it was hard to deny how good looking both men were, and they certainly sent your heart aflutter. After some time, it seems you'd started to develop feelings for both of them. Strange, perhaps, but you couldn't help it. It wasn't just their looks, no, you couldn't help but fall for their unique personalities.
You didn't think either of them would like you back in that way, though. This belief was, in your eyes, reinforced when he agreed to go out with one of his fellow third years. She looked like she was a model, really, how could you even compare?
It was her nasty attitude that drove you away. Oikawa had told you he'd accepted because she was pretty, and it sure showed that he knew nothing of her personality. She was spiteful - jealous even, she'd get in your way as much as she could to prevent you from seeing him. It made you sad, but as long as he was happy with her...
You lost track of the times you'd somehow ended up at Shiratorizawa or Ushijima's place. It surprised him at first, but eventually he'd get you to bawl your eyes out and tell him your troubles. Ushijima never saw Oikawa as his rival, be it in volleybal or in love.
You were snapped out of your thoughts when the whistle rang. They'd won. Shiratorizawa had won 2:0, and you saw how defeated Oikawa was. Naturally, his girlfriend was nowhere to be seen. She'd stated she didn't like volleyball before.
Unbeknownst to you, Ushijima and Oikawa had had a little run in before the decisive match. Oikawa had taunted him like he usually did, but Ushijima could feel something resembling... jealousy behind his words. And so, he said the only thing that seemed logical, at least to him.
"You don't deserve her. After I defeat you, I'll tell her how I really feel."
Ushijima had walked away without a second thought, leaving Oikawa in a sort of trance. He felt himself panicking. He didn't plan for this to ever happen. He only realised how he felt about you when he felt how little he cared for his current girlfriend, and how much he missed your presence. Was it too late?
Ushijima had caught you in the hall, just as you were picking up his and your favourite drink from the vending machine. You held it out to him with a smile. He thanked you and took the drink from you. The two of you sat in the hallway, quietly sipping your drinks next to each other. The silence felt a little awkward, so you decided to speak up.
"Ushijima-senpai, congratulations on--" you began, but he suddenly turned towards you and grabbed your free hand. You let out a yelp in surprise.
"I... (f/n), you're..." he spoke, obviously struggling with his words. This was the first time you'd seen him this nervous.
"I care about you, more than you'd ever know. I think... no, I know that I've fallen for you. You know I will treat you well, so please, be mine."
Your face heated up more than ever before, not knowing what to say. Did one of your long term crushes just confess to you?! Moreover, how long had he been feeling that way about you?!
Ushijima noticed your silence, and spoke up. "It's fine if you can't answer me now. Go home. Answer me later."
You'd spend the rest of the week feeling very confused. You decided to turn to the other person you were - or at least, used to be - closest to. Oikawa.
"Can I speak with you privately, Oikawa-senpai?" you'd asked him, making sure his girlfriend wasn't near. He seemed to be in a great mood, although you didn't know the reason for it. Oikawa assumed that since you were talking to him again, and that he hadn't seen you and Ushijima hand in hand yet, that you must've rejected him. He thought you'd come back to him, finally.
"Ushijima-senpai, he... asked me out recently," you said. Oikawa suddenly felt very nauseous. "Do you think... that I should go out with him?"
Oikawa had no idea why you were being so nonchalant about this. Didn't you ever notice his feelings for you...?! Didn't you see how he looked at you whenever you wouldn't speak to him? Ah, of course, he still had his girlfriend... of course you couldn't know that he felt nothing for her.
"No," came his answer. You turned to look at him, and came face to face with an expression you'd thought you'd only see during his matches. "I do not want you to go out with him, at all."
Despite Oikawa's statement, you'd ended up accepting Ushijima's confession either way. Word spread quickly, and soon most of those involved with volleyball had come to know about 'Ushijima's wonderful lover'. You'd figured your relationship wouldn't stay hidden for very long when dating the very man picked to represent Japan.
Still, you couldn't deny how hurt you felt whenever you passed or spotted Oikawa, giving you a look that very much matched the face he made when his team had lost that faithful day.