Baryon Mode

is a unique transformation accessible to Kurama and its jinchūriki.

Overview
In this state, Naruto's hair becomes spikier, standing up on on its ends with tuffs on each side of his head appearing as fox ears. His whisker markings become thick with the upper ones on each side curving up below his eyes. The pigments around his eyes become black and stretch up towards his makeshift fox ears and he takes on Kurama's red-slit eyes. The coloring of his clothes turn orange and the front of his cape over his chest gains a black swirl surrounded by six lines. Flowing from the back of his cape is four orange chakra tails and five more at the end of the cape; each tail has a black line down the center that connects in the middle of the cape as a swirl.

In a process similar to nuclear fusion, Naruto's and Kurama's chakra are consumed as raw materials to produce a new type of energy. The increase in chakra was enough to shock both Isshiki and Sasuke, with the latter noting it being tremendous. When in use, it dramatically boosts Naruto's reflexes, speed, and power to such extremes that he even surpasses Isshiki's capabilities, allowing him to snatch the Ōtsutsuki's black rods out of the air before they are visibly enlarged, dodge and effortlessly parry attacks.

Because of the extreme risk of death due to its energy consumption, Kurama warns Naruto to not make any unnecessary movements, nor act on any stray thoughts, telling him to focus on only the most calculated of moves to keep Baryon Mode activated as long as possible. Kurama notes that the Baryon Mode reduces the user's lifespan, and because all chakra is connected, contact with an opponent will drain their lifespan as well.

Trivia

 * Baryons are heavy subatomic particles that are composed of three quarks. The most common examples are protons and neutrons, which are the particles that undergo fusion in the Sun.