WARNING: The following contains spoilers for Boruto: Naruto Next Generations Episode 181, "The Vessel," now streaming on Crunchyroll, as well as for manga chapters not yet adapted to the anime.
Since Boruto began, fans have wanted to see Naruto cut loose against his son in battle. He's been busy with Hokage duty but lately, he has been paying the wily Boruto more attention. After they beat Momoshiki, he promised Boruto they'd have a real sparring session someday as they truly appreciated and understood each other more.
Now, that day has come, and it's one of Boruto's most anticipated outings ever. However, while Episode 181 finds the two Uzumaki warriors facing off, the bout doesn't go according to plan, because the winner cheats his way to success.
Boruto's been upgrading his talents for quite some time, especially after the Deepa beatdown. He's trained with Sasuke and Kakashi a bit more, leveling up his Rasengan although he knows his new one's taking a toll on his body. As he squares up against his dad, Boruto stuns Naruto by using other natures of chakra, generating not just small Rasengans, but also using wind vortexes, waves and lightning.
Naruto can't believe how fast his kid's growing up, but there's something shady to his defense as he uses his arm to keep sucking in all the jutsus. Boruto's perplexed but little does he know this is Naruto's prosthetic arm, which the science department engineered. They modeled it after Momoshiki, who could absorb moves, but Naruto can't amplify and shoot them back like that villain.
The leader didn't let Boruto know as he wanted to test the hand out in a real fight, not just a sparring bout. When he throws up a dirt wall to block off Boruto's attacks, the hand gets stuck in the wall encouraging Boruto to see what it's about. But it's a mere distraction as Naruto appears behind him, knocking him on his butt and winning the duel. This doesn't sit right with the teen, though, because as he discovers the truth, he tells Naruto that's cheating.
They were supposed to use their natural chakra abilities, not tools, which is something Naruto blasted Boruto for when he immaturely used scientific tools in the Chunin Exams. It's an advantage an honorable shinobi shouldn't be using, but from his actions here, Naruto's a liar and a hypocrite in his son's eyes. The fact he brushes it off irks Boruto. Shikamaru and co. only care about how the hand fared in the fight, angering Boruto even more as he feels like his concerns aren't that important to the council.
No matter their double standards, Boruto makes it clear he doesn't believe in sinking so low and bending the rules again, so clearly, he's learned his lesson and will always fight clean.