WARNING: The following contains spoilers for Boruto: Naruto Next Generations Episode 167, "Their Decision," now streaming on Crunchyroll.
The Boruto anime has found Team 7 at its lowest after Kara sent the merciless Deepa to retrieve the Hashirama Cell. The kids thought they could take the assassin on, but unfortunately, Deepa -- as part of a wider rampage -- almost killed them, with the ninjas barely escaping thanks to Mitsuki's last-ditch heroics.
As they nurse their injuries back home, while Mitsuki's attended to by Orochimaru outside of Konoha, Boruto makes a major leap forward in his career when he targets the perfect mentor. As much as fans hoped it'd be Naruto, it's someone much better suited to the job: Kakashi.
As ideal as it'd be for Naruto to train his son, their personalities just don't match right now. Boruto is impatient and impetuous, whilst Naruto needs someone who'd listen to him in his older years. Bit by bit, they're learning to work together, but it'll take a while before a long-term mentorship could work on a more consistent basis. Given how busy Naruto is, Boruto doesn't want that to happen anyway. He knows the Hokage has to protect the entire village, and he'd feel like his dad is being taken away from a bigger mission.
Kakashi knows how to handle different personalities and temperaments. After all, he worked with Itachi and trained Naruto, Sasuke and Sakura -- a very eclectic mix. When Boruto recovers, he and Sarada vow to level up, and immediately Kakashi starts sensing something bad is going to happen. It's the series' comedic way of foreshadowing what's to come because while he and Naruto had a father-son relationship, Naruto often drove him crazy -- and Boruto will certainly do the same.
That said, Kakashi is an ideal mentor figure. Kakashi simply understands the man beneath the warrior surface, and with Boruto wanting to hone his Rasengan, there's no one better to train him. Kakashi actually taught Naruto to perfect this move, just as Naruto's dad Minato taught it to him. Kakashi was not only close to Naruto's dad, but he was a fan of Naruto's godfather Jiraiya. In other words, he's been part of everything that informed Naruto's family, and while Boruto seems reckless, Kakashi worked to finesse similar elements in the past with Naruto. He'll know what similarities he can turn into strengths and what weaknesses can be reduced.
Kakashi, who handed the Hokage job to Naruto, knows exactly what traits to mold, and he adapts his teaching methods to his students. Whatever differences Boruto has from his dad, Kakashi can hone and help him maximize his potential. It'll be hilarious watching their rapport, though, because Boruto can get even more annoying than Naruto, making teaching him the ultimate test for Kakashi.