Keith appears as the primary antagonist in the movie The Prince of Tennis: Eikoku-shiki Teikyū-jō Kessen! He is an English tennis player from London and serves as the leader of a street tennis group known as Clack or Crack, which operates from a hideout called the King of Kingdom, an old castle. This gang consists of players who have been banned from official tennis competitions and deliberately uses violence to injure and defeat tennis players from schools and clubs.

Keith has a well-built, toned physique with blonde hair and blue eyes. His backstory reveals that he was once a caring individual and a dedicated doubles partner to his close friend, Xiu or Siu. Their partnership came to an end during an official match when Xiu was injured by opponents. In response, Keith struck a shot that sent an opponent flying, an act that led to both players being banned from tennis clubs. This expulsion from the professional tennis world, particularly because his playing style was considered unacceptable, twisted his personality. He became a sadistic individual who channeled his anger and resentment into leading his gang in attacking other tennis players, developing a deep hatred for the official tennis establishment.

Despite this cruel exterior, Keiths original nature resurfaces through his relationship with Xiu. After Xiu left the gang, Keith and his members hunted him down. This conflict is central to his role in the story, which involves targeting representative players from various countries. The climax of his character arc occurs during a dramatic match with Echizen Ryoma. In this encounter, Xiu returns a ball to protect Keith, demonstrating a renewed bond. After losing to Ryoma, Keith undergoes a genuine change of heart, abandoning his violent ways and reconciling with Xiu. The movie concludes with the two friends looking at the River Thames together, having restored their friendship.

In terms of tennis ability, Keith is naturally left-handed but deliberately plays with his right hand, reserving his dominant hand for when he becomes truly serious. This switch is necessary to activate his signature technique, Gemini. Gemini allows Keith to form spheres of air in his free hand that mimic the feel of a tennis ball. He launches this air ball at an opponent just before hitting the real ball, which skews the opponents timing and pushes the racket back before they can properly strike the ball. The force behind his version of Gemini is powerful enough to fling players into walls. He has developed a completed form of this technique called Bio-Magnetism, which accumulates a larger mass of air or ki in the ball and releases it with the force of a wall, specifically designed to injure opponents and prevent them from playing tennis again. This technique is also referred to in some sources as Universal Gravitation. Beyond these special moves, Keith is noted for his speed and accuracy on the court.