Haru is ten when Rin smiles at him, feral and bright, and says, "I'm going to marry you one day."
Haru frowns at him. "Why would you want to do that?"
"Because I like you," Rin says, as if it's obvious.
Haru's frown deepens. "That makes no sense." He likes Rin, but it doesn't necessarily mean he wants to marry him.
It's Rin's turn to scowl. "'Course it does! I asked my sister, and she said."
Haru doesn't point out that, being a year younger than them, Rin's sister is hardly more qualified than them to define what does and doesn't constitute a reason for marriage. Instead, he snaps his goggles on and pushes off of the wall, pretending Rin's surprised shout and ensuing clamber to catch up with him doesn't make his stomach feel weird and his head feel light.
He is eleven when Rin takes his face between his hands and, very seriously, leans forward until their lips are just barely touching.
"What are you doing?" he asks, and it's kind of muffled because Rin's face is in the way.
"I'm kissing you. Duh," Rin says, rolling his eyes. "It's something my sister told me about. Now shut up, I need to concentrate."
Haru holds still, squinting in the late-afternoon sunlight, as Rin presses closer. "There," he says when he's done. "How was that?"
Haru thinks about it for a second. "Wet," he admits, licking his lips, and Rin's face takes on a stony look.
"You try better," he sniffs, toe scuffing the ground with a vengeance.
Haru thinks that he maybe hurt Rin's feelings. But it was still wet. "What if you practice?" he suggests instead of voicing his thoughts, and the transition from sour to enthusiastically hopeful on Rin's face is almost funny.
"With you?" he asks, eyes shining a bit too brightly.
"Sure," Haru agrees, and Rin lets out a shout, surging forward and kissing him again, and Haru's stomach feels like it's full of butterflies; light, jittery, and completely out of control.
He is twelve when they win the relay and bury their trophy. Rin at least waits until they're alone in the locker room to kiss him again, and Haru has to admit that it's a little less wet than before, but that might be because he's already soaking by comparison.
Rin reminds him (again) that he's going to marry him when he gets back from Australia for good, and then he's gone.
He is thirteen when he hurts Rin.
He is fourteen, and fifteen, and sixteen, and he is alive.
He is seventeen when Rin pulls him angrily across the pool lane dividers by the goggles hanging around his neck and kisses him, and it's no longer a chaste press of lips against lips from their childhood. Haru's not quite sure what changed, but there's tongue and teeth and he's kissing back just as fiercely until he's out of breath and gasping confusedly against Rin's lips, staring at him and wordlessly asking why.
Rin leaves without explanation, without even looking over his shoulder, and Haru tries to ignore the pang in his chest just as he tries to ignore the questioning looks being shot at him by Makoto and Nagisa.
He is seventeen when he lies awake in his bed and touches a finger to his lips almost absently, then murmurs, "marry me, huh?"
