Apply standard Naruto disclaimer here.
inspired by Ate de Anquis' fic, The Greatest Criminal.
Gai doesn't hate Naruto, nor does he Sakura. He only hates Uchiha Sasuke.
Gai doesn't hate Naruto, nor does he Sakura.
He likes Naruto, because his cheerful personality and his unhealthy obsession for ramen noodles, always end up making his eternal rival loosen up a bit at the edge. Sometimes, Naruto would manage to pull his sensei down to Ichiraku ramen bar for lunch sessions or two. Other times, a simple flash-up of his thumbs, and a goofy grin, would be enough to incite a similar response from the man that was Hatake Kakashi.
He's fine with the idea that Sakura makes Kakashi a little more complete as a Sensei as well. Even though Kakashi focuses the least on Sakura and her abilities, one can still tell when Sakura makes Kakashi's day when she first showed off her potential to control Chakra. Or the other time when she managed to fend off the Genjutsu around her. Sometimes, Sakura passes by Kakashi's side when Gai is with him, and she'll offer her sensei the cherry blossoms she's picked up along the way.
Gai remembers how these two pupils of his eternal rival makes him...more complete as a Sensei. How the likes of the two of them adds joy and colors in Hatake Kakashi's life. How they make him feel like he hadn't failed as a Sensei, as a jounin, as a person. How they sort of validated his existence, showed him he still had a purpose to live on in life. How they could possibly sum up into the roles of 'important, precious people' in Kakashi's life.
And this is precisely why Gai hates Uchiha Sasuke.
Because he knows Sasuke has topped Naruto and Sakura in all the above mentioned deeds, and he himself had never known the importance of the role he acted in Kakashi's life.
Unknownst to him, he had been the spectrum of colors more so than Naruto and Sakura. He had been the one to bring Kakashi more pride and purpose, and he had never been the least aware of it. He, ironically as the Uchiha sole survivor seeking for his purpose in his life to validate his existence, had in turn helped Hatake Kakashi validate his as well.
But Gai hates Sasuke, because that boy does not even know either of these, and continues to live in oblivion.
Gai has known Kakashi for a long time, enough to know that the boy himself does not trust easily. That boy has known enough bitterness in his life to shun people, to stop placing expectations and hopes in people. For Kakashi had expected his father to come back home, but never did. For Kakashi had hoped his best friend who had died would come back, but never did. For Kakashi had hoped that he hadn't been such a bastard to lose all his important people, but did.
Hence, Kakashi had simply lost all hopes in people.
Until Uchiha Sasuke came along.
Kakashi denies it, but Gai is Gai, after all. And contrary to beliefs, he sees alot of things, and can tell. He knows what his eternal rival is feeling when he decides to teach Sasuke the Chidori. He deciphers the look on the Hatake's face when he watches his pupil execute it on the sand nin when others were not capable of. Because simply, his eternal rival was beginning to feel very much like Gai.
The feeling of pride, the feeling one experiences when he watches his own prized pupil with the swell of the heart, the quickening of the pulse. And Gai knows why Kakashi tries to deny it, tries to deny that he has hoped for Sasuke to succeed his Chidori move, hoped for Sasuke to excel beyond his potential.
Because if you don't hope for too much, you don't experience pain when you lose it.
But, sadly, Gai, too, knows that Kakashi had fallen prey to this statement as well. So Gai watches on, as a quiet spectator, when Kakashi lectures Sasuke and ties him to the tree, when Kakashi teaches Sasuke the easier way to execute Sharingan without excessive use of Chakra, when Kakashi favors the boy over Naruto and Sakura.
And Gai does not have to learn. He knows, that his eternal rival has defied his own mantra of life, of not believing, of not trusting, of not hoping anymore than he is capable of, in people.
For Kakashi had hopes in Uchiha Sasuke.
For that Uchiha boy had become Kakashi's pride, and part of Kakashi himself.
In plaintive terms, Gai would define it in a way, that Uchiha Sasuke was becoming so much of a pride to Kakashi, that he was beginning to shape the jounin's purpose and existence as well. Pride for the Uchiha boy was a driving intention of Kakashi to validate his existence. Imparting all he knows to that Uchiha boy gave him purpose.
And Uchiha Sasuke, unknownst to him, has defined part of Kakashi.
So, when Gai stands by Kakashi's side watching the Chuunin examination unfolds, hears him with the usual toneless, low voice telling the rest who are still gaping in shocking awe at their blatant late arrival, that they haven't been late for no reason, Gai worries, especially more so when Kakashi warns everyone about Sasuke's Chidori, "You're going to wet your pants."
For there's the distinct pride in his tone that cannot be missed, never mind his monosyllabic choice of articulation.
And Gai, testily, tells Kakashi. In his own perculiar way of confirming his suspicion, the worse of it. "It was a dangerous thing to teach your pupil that."
When Kakashi responds with his usual lazy eye that depicts he couldn't be bothered at all, "Didn't you do the same as well?", it deepens Gai's worry by multiplied folds. For Kakashi had just compared himself to Gai, and Uchiha Sasuke to Rock Lee.
This means Kakashi had finally refused self-denial, and went on to betray his life's mantra, placing hopes in Sasuke to succeed his place one day. So much so that Sasuke to Kakashi, now played a role as important as Lee was to Gai.
And that scares Gai, because he knows, the more you get your hopes up, the more painful it gets when you lose it. And the more you acknowlege something, or someone, that validates your existence, the more you desire to protect it, so it'll never get lost, and you won't ever cease to exist.
But Gai has no right to stop Kakashi, just as Kakashi has no right to stop Gai from favoring Lee. Because when Gai sees Lee, he sees himself as he was as a twelve-year old boy. And that goes the same for Kakashi as well, Gai thinks, because when his eternal rival simply looks at Uchiha Sasuke, he is shown a mirror image of himself as a twelve year old.
That's why Gai hates Uchiha Sasuke.
Because he knows Kakashi well, and when everyone thought there was nonchalance in the way he had tied Sasuke to the tree and lecture him on using Chidori on Naruto, Gai knows otherwise. He also knows that when Kakashi had returned to Konohagakure no Sato with Naruto on his back and the absence of Sasuke glaringly notable, he has comprehended the depths of the non-Sharingan good eye with the ease like no other.
Gai is Kakashi's eternal rival. But most importantly, Gai is Kakashi's friend.
And that's why Gai hates Uchiha Sasuke.
Because unknownst to the boy, when he had walked out on the village, on team 7, he had also walked out of Hatake Kakashi's life.
They say, the more you allow someone to define your existence, the more they have the ability to hurt you.
And Sasuke had done that in his case, for he had gone, and broken Kakashi.