• English / United States: Clayton
• Japanese / Japan: キジュウロウ
• Japanese (Romanized) / Japan: Kijūrō
• Japanese (TL) / Japan: Kijuro

Clayton is a Pokémon Trainer specializing in martial arts who lives in a forest close to Daybreak Town. He has been training together with his partner, Mr. Mime, for many years, and they have even traveled through many regions in order to improve their skills. He has since settled in that particular area, which he uses as his field to eagerly train against other Pokémon and achieve even higher goals.

Impressed by the way Ash's Buizel saved Gible, he challenged Ash Ketchum to a battle. Clayton's Mr. Mime proved to be stronger than Ash's Buizel, and it managed to dodge its opponent's Aqua Jet and SonicBoom attacks by skillfully using its Psychic and Double Team moves. It then knocked Buizel out with a powerful ThunderPunch. Ash Ketchum and Buizel, determined to make up for the loss by getting stronger, started training with Clayton's help so that Buizel could learn a new move; Ice Punch. He told them that, in order to master the move, they had to work on improving their speed and concentration.

At first, the progress of Ash's Buizel's training seemed to be really slow. However, after training overnight using unstable and light objects as targets for its punches, like floating leaves, Buizel managed to master the move completely. After the completion of Buizel's training, Ash Ketchum challenged Clayton to a rematch, and Clayton accepted. Ash's Buizel proved to be more of a challenge for its opponent, Mr. Mime, this time and after activating its ability, Swift Swim, in the midst of the battle due to a sudden rain, Buizel managed to increase its speed and finish Clayton's Mr. Mime off with a powerful Ice Punch. Clayton then acknowledged Ash's Buizel's improvement and praised its skills, but also put emphasis on the fact that Buizel still had a long way to go and had to keep on training.

Clayton makes weird abbreviations while speaking, like AshPika (short for Ash Ketchum and Ash's Pikachu), AshBui (short for Ash Ketchum and Buizel), DawnPip (short for Dawn and Piplup) and BroBree (short for Brock and Pokémon Breeder), as our heroes noticed when he introduced himself. Both he and his Mr. Mime really enjoyed Brock's meal, which he prepared after Clayton's first battle with Ash Ketchum.