WARNING: The following contains spoilers for Chapter #53, “That's Reality,” of Boruto: Naruto Next Generations by Masashi Kishimoto, Mikio Ikemoto, Ukyo Kocachi, Mari Morimoto and Snir Aharon, now available in English from Viz Media.
The Boruto manga truly shaped Isshiki Ōtsutsuki as Naruto's most formidable ally. With his war for Kawaki's soul pushing Naruto to the limits and forcing him into Baryon Mode, it became clear he was way deadlier than Madara, Obito Uchiha and even Kaguya. In fact, despite Naruto's dangerous power-up, Isshiki still had the upper hand, making fans think that Naruto would surely be murdered in the process of trying to save Kawaki from becoming the alien's rebirth vessel.
However, come Boruto Chapter #53, Team Konoha brings home the ultimate victory when Kawaki's quick thinking and devotion to the Hokage kills off Isshiki and proves Kawaki belongs in the Land of Fire.
In the last chapter, Isshiki latched onto Kawaki's chakra signature and teleported him to a mysterious space-time dimension to implant the Karma mark once more. Seeing as his life essence is depleting, Isshiki needs to make Kawaki his vessel again ASAP, but Sasuke uses a special mineral bomb that allows the boy to flee. A game of hide-and-seek ensues and unfortunately, Isshiki beats down Sasuke and Naruto to ensure they can't intervene.
As for Kawaki, he's petrified as Boruto has also been taken out of the equation. Now, it's just him and his adoptive dad, and all the memories of abuse back in Jigen's lair come rushing back. With mere minutes left before he dies, though, and even as undetectable as Kawaki is right now, Isshiki holds one trump card -- and he uses it brilliantly. Isshiki demands that if Kawaki doesn't come out, he'll kill Naruto. The Hokage and Sasuke urge Kawaki to run and make the sacrifice but Kawaki remembers how much of a dad Naruto has been to him.
This sense of loyalty throws a wrench into the plan as he doesn't want to live in a world without the kind, compassionate Naruto. As a result, Kawaki comes out of hiding and Isshiki grabs him, putting the rebirth mark on him once more. Everything the shinobi squad has worked so hard for comes to naught, and as he starts crumbling. Isshiki takes pleasure in knowing that soon Kawaki will produce his most perfect and powerful form.
But Kawaki has a huge secret of his own, which Isshiki realizes as he starts to fade into dust. He doesn't feel the connection of the mark, and the big twist is that this isn't the real Kawaki. It's a shadow clone -- the doppelgänger technique he learned from Naruto and Boruto. By the time Isshiki realizes he's been duped, though, he's already fallen to his knees, weak and dying. The real Kawaki emerges atop a rock and as the clone disappears, he jumps off and stomps Isshiki to ash, killing him for good.
Naruto and Sasuke are both super-proud even as Kawaki says it took all his energy as he's yet to perfect the jutsu. Still, it paid dividends. Kawaki wants to be a Konoha shinobi and while Isshiki laughed at this ambition, Naruto's happy he has another son and trainee. As for Isshiki, seeing as he doesn't have a replacement body, this is the end for him, and now the heroes will shift focus to erasing the final stains of the Kara terrorist cell.
