When Rei was six his mother took him to the doctor. He doesn’t really remember much, just the cold press of the stethoscope to his chest and his mother’s worried smile and the lollipop he got afterwards. The doctor let him listen himself, though, he knows; he remembers that part, the weird feeling of the wire in his ears and then the knowledge, however impossible for his little brain to understand, that that was his own heart in his ears, a thump-thump-flutter of life a little off-tempo.
Nagisa’s still breathing hard next to him, but the only thing Rei can hear is the butterfly fluttering of his own heart in his chest.
“You saved my life,” he says, or tries to, the words mixing up in his mouth and mostly lost in coughing anyway. He slumps forward with the weight of it and Nagisa catches his shoulders, peering up at him through the sodden tangles of his hair, his eyes huge and worried.
“I’m sorry,” Rei says softly, closing his eyes and trying to catch his breath. His limbs feel like lead, all beauty and strength sucked out of him by the sea.
Nagisa doesn’t say anything, and Rei opens his eyes, thinks maybe he hadn’t managed to speak intelligibly after all, and tries again. “I’m sor—”
Nagisa leans in and slots their mouths together, his hands coming up to cradle Rei’s jaw.
Rei makes a noise—pretends, for the sake of any dignity he might ever have again, that it’s just the end of the word—and kisses him back, because. This. This wasn’t the plan, this isn’t in his calculations, but god if it isn’t the best feeling he’s ever had, boneless with relief and thrumming with surprise and Nagisa’s perfect soft mouth against his.
His hands come up almost without his permission, would fist in Nagisa’s shirt if Nagisa were wearing one but just end up tracing hesitantly over his chest, and, fuck, he’s shaking, they’re both shaking, and thunder booms deafeningly close and then they’re clinging to one another, now too close to be kissing and still shaking and Nagisa is so warm against him, steady and warm and he saved Rei's life.
“Um,” he says, half into Nagisa’s throat and half into his hair, and Nagisa presses a kiss to his temple, humming a little, happy and hysterical all at once.
“Um,” he says again, and Nagisa pulls back enough to look at his face, smiling.
“Sorry, Rei-chan,” he says, not looking sorry in the least, “I just really wanted to do that.”
“N-no,” says Rei, “it’s really—very alright.”
Nagisa shifts, and he’s really just in Rei’s lap, now, all warm slick skin. “Is it,” he says, eyes twinkling, and leans up to press tiny kisses up Rei’s jaw. “So it’s fine,” he says between nips, “if I keep going?”
Rei gulps humid air, wonders, maybe, if somewhere he’s still drowning. He slides his hands up Nagisa’s back, tracing patterns through the droplets of water clinging to his skin. “Please,” he says.
He can feel Nagisa grin against his ear. “Told you. Deserted islands are always a good idea.”
Rei rolls his eyes and curls a hand around the back of his neck, shifting so he can kiss him properly. He tastes like seawater and sleep and panic, and Rei has never been happier to be alive.