"Fū" is an extremely fast swing that is based on a sword-drawing technique. The fast swing means that the opponent can neither see the racket or ball after it is hit, making the ball seem 'invisible' to the eye. This shot often returns the ball before the opponent has even recovered from the previous shot. This is the move on which the "Invisible Swing" was most likely based in the anime. Due to the nature of the Fū Rin Ka Zan, Fū can be used to counter the Ka technique. In the New Prince of Tennis manga, it was revealed that Sanada can incorporate "Fu" into his footwork.