"No!" Naruto bellows. "I had to find that out on my own! What the hell? I ask him all the time to train me outside of team stuff, and he never does. It's always like, 'if I have time,' but he never has time. I never knew he was training Sasuke-teme. This sucks!"
Rather surprised by the unexpected outburst, Kurenai searches for the best words to ease the irate genin. Knowing Kakashi's bloody history, Kurenai understands the senior Jōnin is likely experiencing some form of shame-birthed debt toward the last Uchiha. Deep regret over his fallen teammate, Obito, which Kakashi likely feels he can only atone for through personally training and guiding Uchiha-kun. While there may be an understandable reason, Kurenai can't help but feel for Naruto. In the boy's eyes, it just looks like favoritism toward his class's Rookie of the Year.
"Well, Naruto," she starts, deliberately using his name to calm him a bit. "It seems to me like you're going in the right direction. Mastering chakra control is absolutely key to becoming a great shinobi. There isn't a great warrior alive who has terrible chakra control." She adds an easy smile but it barely phases the upset blond, so she continues, "also, I bet Uchiha-kun can't use Kage Bunshin. It's a difficult technique to learn, not to mention very dangerous."
"Huh?" Naruto abruptly questions coaxing him a little out of agitation. "Dangerous how?"
Kurenai pauses again, wondering if this blond oddity is actually using a technique without knowledge of its harmful disadvantages. "The physical ramifications of dispelling your clones." At his blank stare she continues to further explain, "after the amount of information or experiences is transferred back to the original, it affects you physically in harmful or potentially lethal ways. It can easily be too much for the mind to handle. Many shinobi have gone insane, destroyed their chakra circulation system, or become brain dead from overuse. Some have even died. It's why Kage Bunshin is a forbidden jutsu and any shinobi that can use it are warned to never keep it active for longer than ten to fifteen minutes."
"Huh, I didn't know that," he comments noncommittally.
"How could you not know the side effects of such a dangerous jutsu? Didn't Kakashi-sensei warn you how overuse could kill you?"
"Mnn, now that I think about it, I don't remember him ever telling me about that," Naruto ponderously feeds back. "But then again, I keep my clones out for way longer than fifteen minutes, so I never bothered to ask him."
Setting aside Kakashi's potentially fatal negligence, she focuses on his declaration of, 'way longer than fifteen minutes.' "...How much longer?" she asks, growing more and more vexed by this conversation. It's either an extreme lack of guidance and responsibility on Kakashi's part, or this blue-eyed blond is a baffling fool.
"It varies really," he starts, garishly chewing on his steak with a happy hum. "But generally for several hours, like five or six, I guess," he easily answers.
"That's not possible," Kurenai staggers to say, eyes wide with healthy skepticism. "You've would've long been brain dead, if not dead-dead after half an hour!"
"Uh, I don't know about all that but I always have clones training," Naruto tells her. "Even before we... you know, I sent out twenty clones to train and only dispelled them a couple minutes ago."
Kurenai had long since put her utensils down, in awe at the tremendous discovery she stumbled upon, but now she has to get up and pace, only stopping to make absolutely certain. "You're sure?"
"Sure about what?"
Frustrated, she answers, "that you can keep your clones activated for more than five hours!"
"Oh. Yup," he answers.
She paces again but remembering her hunger she picks up her plate of salad for the ride and eats as she paces. "Do you still have a headache?"
"Nope," he answers after swallowing his cut of steak. "Gone already."
"Amazing," she gasps, ignoring his happy chuckles. His body must be highly abnormal to be able to deal with such drastic side effects. The only theory she can think of thtat might provide an answer is the power of the Kyūbi, but she doesn't know nearly enough about that to make any educated conclusions. "This means that any experience or knowledge your clone... Kami," she gasp in awe. "With enough clones you could learn techniques that normally require years of training in a matter of weeks."
"Yup," Naruto calmly answers, focusing more on his steak than Kurenai's amazement.
Recalling their chase from his apartment, she asks for confirmation's sake, "have you learned Tree-walking?"
"Yeah," he answers between chewing.
"Water-walking?" she quickly asks.
"I fight against my clones on water all the time," he responds with a smile. "It's better than hitting the ground but man, am I tired afterward."
"Amazing," she answers letting out a huff of air. "So, what are you working on now?" It's the first time Kurenai has ever felt excited talking to Naruto. She just couldn't deny the ambitious sensei within was enthusiastic to hear his response.
A look of hesitant nervousness blooms across his face. "Sorry, Nai-ch- er, Kurenai-chan," she rolls her eyes at his slip as he continues to say, "it's sort of a secret right now, but, I can tell you it's really awesome!"
"I don't think you realize how amazing this is Uzumaki-"
"Naruto!" he interrupts. "Everyone calls me Naruto."
"…Naruto," she easily concedes, interested only in advancing the conversation. "With proper guidance, you could be one of the strongest shinobi in the nation." As a sensei and strong inheritor of the Will of Fire, it's not hard, by any stretch of the word, to marvel at his potential and envision his future.
"That's the plan," he exclaims with glee. "Watch, I'm going to be the greatest Hokage ever!"
'…Holy shit!' her mind explodes. It's been soo easy to ignore his thoughtless boasting as delusional wish-fulfillment, but at the moment, there's a real possibility he may, in fact, be able to achieve his dream '…with training, of course. How can that idiot Kakashi ignore this?' To ignore or not see something this massive, Kurenai has to wonder if the silver-haired elite even cares about their village at all. She's big enough to admit she never cared for the boy, but it's not like he's been shy or hiding his desire to learn. It only took her a few questions to see his potential. 'And Kakashi's had so much more time and opportunity to ask!'
Kurenai is already making plans to talk with the copy-ninja when her earlier intent to make sure Uzumaki-kun stays content pops to the forefront of her mind. The blond would obviously feel more grateful, possibly even indebted to her if she helped train him where his own sensei has failed. Though there is a well practiced, yet unwritten rule that states, unless the primary sensei asks for the assistance, then another sensei approaching the student is widely considered unacceptable. It wouldn't be a good situation for Kurenai if her training Naruto ever came to light, but it's not any worse than what they've already done in the dark. As long as everything remains secret, there shouldn't be any issues.