Baryon Mode

is a unique transformation used by Kurama and its jinchūriki.

Overview
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.