The word naisu is the Japanese pronunciation of nice, and in online gaming and VRChat communities it became a playful way to cheer someone on, often typed or shouted after a good play. This triple repetition turns a simple compliment into a short chant, which fits the fast pace of short-form video and livestream clips. Because it is easy to understand even without knowing Japanese, creators keep using it as a quick, positive reaction sound for wins, cute moments and surprising successes.