Gai is Kakashi's friend but rival. Guy is also insanely competitive and challenges Kakashi in many ways, everything from sparring to games like rock-paper-scissors. He believes in the power of youth and is usually hyper and eccentric... and is even secretly jealous of younger people. Though he knows ninjutsu and genjutsu, he specializes in taijutsu. He believes in hard work and stresses that belief with his students, especially Lee whom idolizes Guy and emulates him.

Shippuden

Guy, Neji, Tenten, and Lee aid Kakashi, Naruto, Sakura, and Chiyo in retrieving Gaara from Akatsuki members Deidara and Sasori. Guy and his team are intercepted by Kisame who had a run in with Guy before, but Guy can't seem to remember. Feeling insulted, Kisame starts to torment Guy by placing Lee, Neji, and Tenten in his Water Prison technique. Guy and Kisame fight rather evenly until Guy realizes that his students are drowning, making him release the gates and annihilate Kisame, whom turns out to be a fake created by Pein. He and his team are later confronted by duplicates of themselves in which they have to conquer, later aiding Naruto in trying to capture Deidara who tricks all of them and escapes.

Powers/Techniques

Guy has knowledge of the eight gates, which he taught to Lee. It's a forbidden technique that removes the limits naturally placed on the human body, allowing increased speed and strength each time a gate is released. However, the technique is forbidden because of the great strain and damage it does to the body, the 7th gate could be fatal if used too long and the 8th gate promises a few moments of unrivaled power at the cost of the user's life. The eight gates are:

1st Gate: Opening

2nd Gate: Rest

3rd Gate: Life

4th Gate: Pain

5th Gate: Closing

6th Gate: Joy

7th Gate: Shock

8th Gate: Death

Guy has used "Morning Peacock" where his fists become engulfed in fire, and is able to summon giant turtles.