“Ka-tsu-ya,” Reigen says from his place half on top of Serizawa, punctuating each syllable by poking Serizawa’s chest.
“Mm?” Serizawa says, half-asleep.
“What can you cook?”
Serizawa pauses, to think. He’s used to Reigen’s sudden fits of inspiration, to put it kindly. He offers, not wholly truthful, “A lot of eggs.”
Reigen clicks his tongue. “That’s no good, Katsuya!” He says, tapping Serizawa’s chest lightly with his fist, for emphasis. “How are you gonna sweep me off my feet with a romantic dinner like that?”
“I never thought of it that way,” Serizawa says, trying to keep the smile off his face. “How do you suggest we proceed, oh great psychic?”
Reigen is undeterred by Serizawa’s teasing, though the heat in his face might say otherwise. He twists a little to properly place a hand on his own chest, Serizawa pressing a hand to his back to stop him from rolling off him and, more importantly, the bed. “In my infinite kindness, I will teach you how to cook. You’re so lucky to have me!”
When Reigen looks at Serizawa, he’s smiling the kind of smile that makes his eyes go soft and wrinkled at the edges, and Reigen has to look away again. “Yeah, I am.”
“Sap,” Reigen mutters, burying his face in Serizawa’s side, “Go to sleep.”
Reigen likes to cook.
He didn’t really think of it like that as a kid - a thing to like or dislike. Then he’d gone so long without room or, uh, equipment to actually make anything too complicated, that he stopped thinking about that sort of thing altogether. About enjoying the process of making something. So it makes sense, Reigen thinks, that Serizawa brings that back. Or maybe he’s just becoming a sap, too.
Their arrangement starts fairly simply. Serizawa invites Reigen over for drinks, once, when it’s late and he had no classes and nothing better to do, surely. Purely platonic, normal coworker interaction. Reigen had said yes, maybe too quickly.
Reigen made no attempt to hide that he was checking out Serizawa’s place. No posters, some of those figures you build from a kit in a box, DVDs Reigen wanted to rifle through. Overall sparsely decorated, utilitarian. Reigen had made some comment, like, “I should get you a plant, like a housewarming gift.”
Serizawa had said, “Oh, I try not to be at home much, so I don’t think about how it looks, you know?”
Reigen didn’t really know, but he didn’t really care what his own place looked like.
Of course, he saw the small, cramped kitchen, but he didn’t think to comment on it. After one (half of a) drink, he did think to comment on it. “You ever cook, Serizawa?”
Serizawa said, surprised, “Not really. Nothing too fancy, I guess. Do you?”
“Not at my place. Used to. I should cook for you sometime, that’s a better housewarming gift. Actually makes the house warm.” Reigen said, and laughs at his own bad joke.
He remembers Serizawa looking at him wide-eyed, like Reigen had revealed some great secret to him. Serizawa said, careful in that way he had where he wasn’t sure what he was saying was appropriate, “You’re welcome to, if you’d like.”
Reigen had said, “I might take you up on that, then,” and downed his drink, he doesn’t remember why he did that. He does remember waking up on Serizawa’s couch with an old quilt on him and a huge headache. He left pretty quickly after that, not wanting to bother Serizawa. He leaves a note, at least.
It’s not until he’s on the train back to his shitty tiny apartment that he remembers what he offered.
Reigen ends up on Serizawa’s doorstep a week later, carrying bags of groceries. He knows Serizawa’s home, because he asked if he could come over, to cook. And Serizawa had looked almost happy when he said yes. Probably Reigen was imagining things, though.