(Character description from giantbomb.com)

Guy believes that "hard work without believing in yourself is worthless", and as such trains by repeatedly jumping sideways and hitting mitts in an effort to better himself. Guy, and by extension Lee, lives his life by his own "My Rules" philosophy, which involves setting tougher goals for failure so something good comes of it. For example, he vowed to walk 500 laps around Konoha on his hands if he lost a contest with Kakashi, and proceeded to do so upon losing, even though people stopped paying attention eventually. Lee's willingness to train in the same manner as Guy seems to have caused him to surpass his master's stamina, as by the end of Part I Guy has difficulty keeping up with Lee, lamenting that he is not as youthful as he once was.

Guy is the self-proclaimed rival of Kakashi Hatake. Kakashi, however, is indifferent to their rivalry, which annoys Guy to no end. Guy randomly challenges Kakashi to contests of skill, and has a acquired a record of 50 wins and 49 losses in doing so. Given that the contests that make up this figure are so varied (ranging from Rock, Paper, Scissors to sumo-wrestling), this it is not much of an achievement on Guy's part. Nevertheless, Guy is proud of his record. In his rivalry with Kakashi, Guy has developed an effective counter against Sharingan users: by focusing on their feet, Guy can both predict the movements of the enemy and negate the Sharingan's necessity of having eye-contact. Currently, Guy is the only ninja who can use this technique.

Guy has many mannerisms unique to him in the series that are meant to be seen as corny and old fashioned, a reference to common clichés of "youth" (seishun) anime. He is best known for his "nice guy pose", which consists of giving a thumbs up, winking, and smiling with teeth so white they give the proverbial "ping". This action is often used by both Guy and Lee to indicate commitment to a statement they had just made, their highest form of a promise. Guy's teacher-student relationship with Lee also carries distinct attributes, such as when Guy will punch Lee for a slight infraction of a rule. After Guy assigns Lee an arduous training task as punishment, meant to recapture Lee's focus and discipline, the two may then burst into tears and embrace, in brief regret for the strong blow Lee was given.