Ryohei learns fairly early on in life that strength is coveted and admired and even feared; likewise, weakness is mocked and pitied and undesirable. He learns this lesson in blood and bruises and broken bones. However, he grows up alongside Kyoko, the epitome of kindness and gentleness and all things good, and he knows that physical strength isn't all there is - that beating your opponent senseless is all well and good, but it's ultimately meaningless if there's no real reason for it.
(Kyoko is threatened, and Ryohei utterly loses it. He manages to take down half of them, but he's outnumbered and weaker. They put him in the hospital, and later, he makes a lifetime promise. But he prevented her from any injuries, and he'd do it again, promise or no promise. Protection is as good a reason as any.)
He learns a new word somewhere along the way, and it seems to sum up perfectly his own thinking, his entire being.
Extreme.
Yeah, he thinks to himself excitedly as a whole new world opens up to him, yeah, life should be extreme. Ryohei's never been cut out for mediocrity or normality. There's always this itching underneath his skin, this restlessness that seeps into his very blood - it makes him want to run a hundred laps in under ten minutes backwards or swim a thousand laps with an arm and a leg tied behind his back or even fight a bear blindfolded. He can't seem to sit still, and his attention wavers easily. He shouts a lot, but that's because there's so much to say - and everyone else is usually too slow to respond.
His passion for life is utterly and totally... extreme. He can't think of a better word - or a word he likes better - and so it becomes his go-to adjective for all things worthy. Even his use of the word is extreme. Ryohei is certainly aware of this fact.
He takes all of his energy and eagerness and puts into a sport he's come to love. Boxing is as simple as it is ruthless. Punch the other guy until he admits defeat or gets knocked unconscious. Easy. Extreme. He learns about exercises and straights and lunges, proper stances and cool-downs, the differences between brand names and knockoff equipment. He excels at it, lives and breathes it, and Kyoko approves, which is all he's ever needed.
He rises quickly through the ranks and becomes the captain of their middle school club by his third year, and his team is tighter than ever. They look up to him, and he returns their affection ten-fold. He puts together training menus catered to each member, requests days off from school, signs them up for tournaments. They don't always win, but when they do, he grins so widely that his cheeks hurt - because it's his team now, he helped make all of this a reality, and it's him they congratulate and thank and dog-pile on top of in their own little version of a group hug.
Then Sawada Tsunayoshi comes barreling into his life, along with all of his friends, and suddenly, his free time is no longer spent on solo jogs around Namimori or shadowboxing until night falls. He finds himself wandering to Tsuna's house after school to see what chaos has erupted that day or being asked to participate into competitions between 'families.' Sometimes even Kyouya tags along, and Ryohei knows how difficult and standoffish the guy can be. It's all fun and exciting and undoubtedly extreme.
There are battles he has to fight, now, ones that have nothing to do with official tournaments or appear to be legal by any means. Most of the details go over his head, but he understands the price of defeat. So he trains and grows stronger under Colonello's guidance, and when the time comes, he pulls through and wins. He spectates his friends' fights - with gritted teeth and worry in his heart - but everyone makes it out alive. And eventually, they win the whole thing. Ryohei gets a new ring, a powerful weapon, even if he knows it shouldn't logically be possible. Since when has logic ever applied to him anyway?
There are more battles to be fought and more at stake, and he (and his sister) are somehow in the future. It's extremely insane, but fear keeps him grounded - because it's not just his own life being risked. Kyoko is here, too, and he'll never forgive that future Sawada for bringing her here. To make matters worse, Tsuna tells her the truth about everything, but he's a man - and he makes himself get over it after one punch. Because it's Tsuna, and he thinks of the kid as his little brother.
The intricacies of the situation once again remain a mystery to him, but he knows what he has to do - fight and win. So they do, only they lose Yuni in the process, and Ryohei's not entirely sure he can count it as a completely victory. Nevertheless, they return home (for good this time), and he realizes, maybe not for the first time but fully realizes that his fight will never be over because he's chosen to stick by Tsuna and Kyouya and everyone else. He's never said as much and neither have any of the others, but maybe it doesn't need to be said.
Ryohei's never been cut out for mediocrity or normality, and this life? Yeah, it's pretty extreme.
(Protection is as good a reason as any.)