Naruto's new form is dubbed "Baryon mode" in the manga, and as Comic Book highlighted, it boasts incredible power but at a high cost. Kurama explains that his and Naruto's chakra work together like Nuclear Fusion, which boosts Naruto's power to new levels but destroys both his and Kurama's chakra rapidly. However, since all chakra is the same at the root, it also destroys the chakra of whoever Naruto comes in contact with, such as his foe Isshiki.
It's because of the sacrificial nature of the mode that Kurama asks Naruto if he is willing to die to use the form. The Hokage makes it clear that he has no problem with sacrificing himself for his village. As the battle finally comes to a close, Isshiki is defeated and unexpected sacrifices occur. After the dust has settled in the latest Boruto manga chapter release from Viz, it's discovered that Naruto lives, but Kurama dies. Sasuke is left without his Rinnegan thanks to a possessed Boruto. And now two of the series' strongest powerhouses have been reduced to shells of what they once were at their peak.
