Normally, Iwaizumi Hajime was a deep sleeper. Nothing could wake him up, you could practically fire a gun next to his ear and he wouldn't even flinch. Except for one thing that would always wake up, without a doubt.
Thunderstorms.
Oikawa knew this already, having had his fair share of sleepovers with the other. And some of them had thunderstorms.
The first time it happened, they were still very young. Iwaizumi had tried to live through it, eyes closed and hands pressed to his ears. Usually, he would get out of bed and hide in his parents' bedroom, clinging to his mother for dear life. But she wasn't here now and he didn't want to bother Oikawa. He would be pathetic, laughed at if he cried during a thunderstorm.
A very loud thunder struck, lightning flashing and lighting up the whole room. Iwaizumi had yelped and thus woken up Oikawa. He didn't laugh at Iwaizumi. Instead, he crawled out of his bed, onto the futon Iwaizumi had claimed for the night.
"Don't cry Hajime", he said as he grabbed his hands. "I'll protect you." They had held each other through the storm, Iwaizumi shivering and flinching at every thunder. When the storm was finally over, they fell asleep in the same bed, Oikawa's arms still around Iwaizumi.
Nowadays Iwaizumi didn't need anyone to hold him. He was a third year high school student and could get through the storm on his own. He would grab his phone and listen to music, play some games or browse through social media.
Tonight, however, that was impossible. They were at training camp and his phone was on the other side of the room, charging. He had forgotten to bring his earphones so he couldn't listen to music either. His teammates were all asleep, Oikawa curled up next to him.
There was nothing else to do but curl up as well and press his hands to his ears, it seemed. Gently, not to wake anyone, he shifted under his blankets and clasped his hands over his ears, mouth pressed in a thin line. The thunder got louder with every passing minute, storm coming closer and closer.
Apparently he had made a sound, because when he opened his eyes after a particularly loud bang, he stared at Oikawa's opened eyes.
"Storm again, huh", the setter whispered. Iwaizumi nodded and flinched as the lightning illuminated the room. Without a word, Oikawa scooted closer to the other and reached out his hand to take Iwaizumi's. Another lightning strike, followed by a loud blast.
"Shh, it's okay Iwa-chan", Oikawa whispered and grazed his thumb over the back of Iwaizumi's hand. "I'm here…"
They stayed like that until the rain let down and the thunder had moved away, storm calming down. Completely exhausted from his fears, Iwaizumi rested his head against Oikawa's shoulder in thanks. Oikawa didn't complain when he fell asleep like that, didn't move him either. No one commented on it the next morning, neither of them mentioned anything about it. It was just their routine with thunderstorms.