What's the point of Naruto holding a kunai in his mouth?


"The Flying Thunder God Technique: A Reminder of Minato's Assistance in Battles" The Flying Thunder God technique in "Naruto" enables instant teleportation by planting a seal beforehand.

Despite being the Fourth Hokage's son, Naruto never learned it but acquired the Instantaneous Body Technique instead. 

Naruto biting the kunai holding the Flying Thunder God seal in his mouth is reminiscent of Zabuza Momochi's technique, creating a psychological impact on opponents and reminding Sasuke of the fear from the Fourth Hokage's technique. 

Carrying the kunai symbolizes Minato's teleportation ability, forcing Sasuke to stay cautious, makes Sasuke wary of surprise attacks.