Yamamoto probably should be surprised by the knock at the door of the dojo.
He's only just finished waving his friends off; it's late enough that any sort of celebration is best saved for the morning, and his poor night's sleep and the exhaustion of relief is catching up to him so he's yawning before he's even slid the door shut behind him. And he doesn't expect the knock, at least not consciously, but it's true that there's no spark of adrenaline at the sound, and when he hears the sound he's standing in the middle of the floor, hands idle at his sides and still in his training clothes, as if he was waiting for something yet to come.
Maybe he was, in the back of his mind. He knows Gokudera, after all.
He's smiling as he slides the door open, as sure of the glower that will meet him as he is that the sun will rise in the morning. "Gokudera."
The other boy is hunched forward, his shoulders curled in like he's trying to protect himself from nonexistent rain. His hands are stuffed safely in his pockets, though Yamamoto can see the idle fists he's making through the pockets of his jeans. When he looks up it's his eyes that move, not his chin, and there, that's the comforting familiarity of a frown.
"You okay?" Gokudera blurts, so quickly Yamamoto has to blink and take a moment to gain traction on the question.
"Hm?" Gokudera is staring at him. Yamamoto can see the way his eyelashes catch together at the outside corner, the pink against his lower lip a giveaway for his habit of biting against the soft skin when he's nervous. There's a chain dragging a metallic line over his collarbones, multiple shirts layered one atop the other over his shoulders.
It's hard for Yamamoto to focus on the question instead of the temptation of that metal-marked skin. "I'm fine."
Gokudera blinks, the expectation of irritation in his eyes flickering into something softer and warmer for a moment; then he looks away, down and to the right, so Yamamoto can only see the color rising red in his cheeks and not the actual expression in his eyes. "We were worried, you know."
Yamamoto is good enough at Gokudera-speak to hear the safety of that plural, the speaker for unnamed masses who only ever have one true voice. The affectionate concern is clear even under the gruff pseudo-anger in Gokudera's words, warming some part of Yamamoto he hasn't even realized was shivering.
He doesn't have to think about smiling; the reaction forms easily, curving to fit across his lips until his exhale comes out more like a laugh than a sigh. "Thanks."
Gokudera's eyes flick up, just for a minute. The light behind Yamamoto's shoulders catches on the color, glows warm and soft in the green for the length of a heartbeat. "Yeah." Then he's looking away again, going redder and shifting his weight like he can't quite decide how to align his balance. When he speaks again it's to the edge of the door again. "You gonna be sulking again tomorrow?"
Yamamoto shakes his head without looking away from the line of the shadows throwing Gokudera's features into artistic elegance. "No." He's still smiling. "I'm fine now, Gokudera. You don't need to worry."
"Who said I was worrying?" Gokudera snaps, but he looks up again to fix Yamamoto with another glare so his eyes catch the light again.
The retort is easy. Yamamoto doesn't take it. He takes a step instead, a half-stride so he's standing in the doorway itself. Gokudera tips his head up to hold their eye contact, his blush spreading out farther over his cheeks, but he doesn't move away. Yamamoto can see him swallow with anticipation, can see the shift of his lips as his frown eases into expectant softness.
"Thanks." Gokudera flinches like the gratitude is a heavier burden than a slap would be, but when Yamamoto slowly leans in he doesn't offer any protest in word or motion. His eyelashes shift shadows across his skin, his lips part so Yamamoto can feel the warmth of the other's breathing against his mouth.
Teasing him would be easy. It would take a moment of hesitation, half a sentence of a question to draw a growl from Gokudera, a hiss of frustration and fingers grabbing too-tight at Yamamoto's neck to drag him down. Yamamoto can see the shape of it like it's laid out in front of him, the path he could take if he wanted.
He doesn't take it. He follows through on the movement, crosses the distance to Gokudera's lips without a flicker of a pause, and when his lips touch the other boy's Gokudera's mouth is soft with all the unthought affection Yamamoto is beginning to learn to recognize as much as the aggression. When he takes a breath it takes like smoke and sweet familiarity, and all the newformed doubt in him eases under the reassurance of the other's touch.
Gokudera is better at comfort than he knows.