This is inspired by a couple of the headcanons from the blog daily-okakuri.

It all starts when one of the girls in their dance class starts wearing her hair in long braids. Mayuri is entranced by her twin coils of hair, always asking to play with them and watching them out of the corner of her eye. So Okabe isn't surprised when Mayuri becomes determined to learn how to braid hair.

But Mayuri's hair is too short for braiding, her mother points out, much to her dismay. Okabe saves the day by suggesting a compromise: Mayuri can practice braiding her dolls' hair while she waits for her own to grown out. Mayuri tackles him in a grateful hug, and Okabe accepts the fact the he'll inevitably be learning how to braid as well; he and Mayuri have always done everything together.

Soon they fall into a routine. Whenever they go over to Mayuri's house, she'll practice braiding, and then they both watch TV together. Lately, they've been watching a program about a daring hero that saves the world from the nefarious plans of a dastardly mad scientist. It's comfortable between the two of them. Mayuri is Okabe's oldest friend. Adults often find it odd that his best friend is a girl, and often ask stupid and awkward questions, but Okabe ignores them. He and Mayuri have always been together, and he's not about to let some nosy idiots ruin his closest friendship.

Okabe occasionally tries his hand at braiding, and quickly finds that he's very good at braiding hair; his long nimble fingers come in handy. Mayuri's hair grows fast, and soon she's wearing her hair in braids every day. And although she's been practicing braiding, she loves to have Okabe do it for her. There's something very soothing in the methodical way he braids her hair. He's efficient, but his hands are so gentle with her.

Eventually, Mayuri outgrows her braiding obsession, and begins cutting her hair short again. Okabe will never admit it, but sometimes he misses the relaxing afternoons he spent with her as they practiced braiding, the soft feeling of her hair in his hands as he carefully wove it into braids.

Kurisu pushes open the door to the bathroom, her hair soaking wet and dripping on her shirt. "It's so hot in here!" she complains loudly to Okabe, striding over to the couch and fanning her face. She's in her usual shorts and tights combination, minus the jacket, because it's June and the air-conditioning in the lab is broken.

"Surely my assistant won't be defeated by something like a little heat," Okabe teases, but he's sweating and looks a little red. He refuses to relinquish his lab coat. She sighs irritably and sprawls out on the couch, propping her head on the end closest to him and draping her hair over the edge to stop it from dripping on her.

"Aren't you going to dry your hair?" Okabe asks, running his fingers through her long red locks. He's always loved to play with her hair.

Kurisu gives a pleased sigh, closing her eyes. Okabe continues his ministrations. "Too hot," she says finally and drifts off to sleep, comforted by the feeling of Okabe's fingers in her hair.

When she wakes up from her nap, Okabe is gone and the lab is empty. She picks up the note he left in the chair he was sitting in, which informs her that he's gone out to look for new parts for the air conditioner. She notices that her hair feels different and reaches a hand up to feel it.

She's shocked to find a perfect braid in her hair. The last thing she remembers is the soothing feeling of his fingers in her hair. Kurisu thinks about it for a moment, then laughs. "He's just full of hidden talents," she remarks, watching the setting sun bathe the room in red light.