The trick is to look like he's really trying hard, Hajime has realized.
It's not something he's used to doing, because when he gets challenged to an arm wrestling match by anyone else on his team, it's all about maintaining order, reinforcing all their perceptions once again that he's the leader of the pack.
That the title officially belongs to Tooru, on the court and behind the scenes, goes unsaid—mostly because of the tacit understanding between everyone on the team that Tooru would be absolutely insufferable if it were ever acknowledged out loud. But that's besides the point.
Right now, though, Hajime is struggling. He's flexing hard, biceps bulging; his cheeks are puffed out and his eyes are near squeezed shut and his face is surely red. His whole arm shakes with the weight of his deception.
With a powerful yell, he throws one last bit of heft into his effort—the seesaw of locked arms swings favorably his way and his opponent's sparkly, determined eyes start to widen in uncertainty. But then Hajime relents, and their clasped hands slam down onto the table, the match over, the victor decided. When the dust settles, a loud gasp goes up from the rest of the group.
"Iwaizumi-senpai..." Kindaichi whispers, "...lost?"
Hajime leans back heavily in his seat, wiping sweat off his forehead. "It was hard fought."
Across from him, Karasuno's teeny middle blocker slowly raises his winning hand up in front of his face, staring at it like he has never realized he has hands until that very moment.
"Uwwwoooohhhh..." Hinata squeaks. Hajime isn't sure what that means.
"No way," Kindaichi says staunchly.
Hinata stands up from the park bench abruptly. He thrusts his hand up into the sky, like he's reaching for the sun itself.
"Hwooooooohhhh!" He looks like he might be... vibrating? "Kageya-MAAAA! DID YOU SEE WHAT I JUST DID—"
"WHY ARE YOU YELLING?" Kageyama bellows back.
Hajime puts his hand over his face, hoping he's managing to look weary, or something, and that nobody can see how hard he's laughing.
"I feel it..." Hinata screeches shrilly, grasping his outstretched hand with the other, like he's struggling to contain his newfound strength, "the power... emanating... from within! With this, I can spike... past any wall!"
"Hinata," Hajime says, and Hinata skitters around to stare at him, his round face shining with excitement. "Congratulations."
Hinata's cheeks go brilliantly pink. He rushes to stand in front of Hajime, and then he bows, and bows, and then bows a third time for good measure, bending at the waist so fast Hajime is worried he's going to fall over, or break in half, or at the very least give himself a headache.
"Iwaizumi-san!" he yelps. "I'll be an ace like you one day! I won't waste this opportunity!"
Hajime nods firmly. Very seriously, he puts his hand on top of Hinata's head, ruffling his ridiculous mop of orange hair. "Next time we battle, I'll be victorious."
Hinata's eyes gleam, shining with awe and admiration. He nods furiously, too overcome to speak any further, and then scoots off in Kageyama's direction, most likely to gloat. Hajime grins, watching him go.
"I don't like the look on your face right now," someone says, and he turns to see Tooru approaching with food. It had taken some convincing on both sides (mainly, Hajime and Sugawara working as an efficiently coordinated and hard-to-resist team), but this Karasuno-Seijoh picnic is turning out to be a pretty resounding success.
Hajime takes one of the plates of barbecue Tooru has brought over. "What's wrong with the look on my face?"
"I already told you, I am not signing any adoption papers for that orange demon," Tooru says. "You know we'd have to take in Tobio, too."
"First of all, Sawamura would drown us before allowing that," Hajime points out. "Second, I know how fond you are of Kageyama, so nice try."
Tooru makes a loud scoffing noise. Hajime contents himself with watching Kyoutani scare the shit out of Hinata by standing four inches behind him until Hinata finally turns and notices him looming menacingly. Hajime can't tell if Kyoutani is trying to intimidate Hinata, or pay his respects now that Hinata has bested Hajime in combat. Kageyama not-very-subtly moves to block Hinata with his body, and it turns into a stare-off.
"Why are you indulging him, anyway?" Tooru asks.
"He asked if I wanted to arm wrestle!" Hajime says. "You try saying no to him, I bet you you couldn't. You're a bigger sap for cute things than I am."
"That doesn't mean you have to let him win—"
"Oy, Hinata!" Hajime yells. "You want Oikawa to teach you how to jump serve?"
Hinata's speed is the same off the court as on, and he zooms over to stand in front of them before Tooru can hide, gazing raptly at them. Hajime can already see Kageyama beginning to rumble furiously over in his wake. Tooru might try to kill him in his sleep, but it's absolutely worth it for the look on his face right now.
"D-do you mean it?!" Hinata asks. "Learn from the Grand King himself?"
Hajime chokes. "The what—"
"OIKAWA-SAN," Kageyama shouts, nearly tripping over Hinata in his rush to push in front of him. Hinata elbows him back furiously. "Will you—"
"No," Tooru says immediately. He points at Hinata. "What did you just call me?"
Hinata claps his hands over his mouth. "G-grand King... King-sama—!"
Oh, no, Hajime thinks, as Tooru swells pridefully.
"Chibi-chan," he says, "I'll have you know this is not a privilege I bestow upon many people—"
"I understand!" Hinata says, clapping his hands together in front of his face in utter sincerity. "I won't take it for granted!"
Tooru looks taken aback. Furtively, he glances around... and then also ruffles Hinata's hair, before saying imperiously, "Come along, then."
Watching them go, Hajime wonders if he should worry about the effect Hinata will have on Tooru's ego. He glances over and catches Kageyama's crestfallen expression. Because Tooru turned him down as usual, Hajime wonders, or because someone else is setting for his spiker?
"Oy, Kageyama," he says nonchalantly, "I've been meaning to ask you this for awhile, but—would you mind tossing for me?"
Kageyama looks startled, before he starts nodding just as enthusiastically as Hinata. "Yes! I'll go get a ball, senpai!"
He hurries off excitedly, a smile wobbling its way onto his face, and Hajime shakes his head with a smile. Sure, Karasuno may be their enemy and all that but... the kids, he supposes, are alright.