• English / United States: Koga
• Japanese / Japan: キョウ
• Japanese (Romanized) / Japan: Kyō
• Japanese (Trans) / Japan: Kyo
• French / France: Koga

Koga is a ninja who trains with his younger sister in a large old Japanese styled mansion that also serves as the Fuchsia City Gym. Koga booby trapped most of the building but Ash Ketchum and his friends were barely able to overcome them. Ash Ketchum initially went into the old mansion to ask them where the Fuchsia City Gym was located but was surprised when Koga revealed that he was the gym leader and that they were already there. Koga's personality is a bit bland and very unexciting as he has been spending too much time training. In the Japanese version, Kyō has a stereotypically archaic speech pattern as he speaks with generic "archaic" words mixed into standard Japanese.

First Gym Battle Match against Ash

For their gym battle, Koga suggested a 2-on-2 battle and Ash Ketchum agreed. As Koga sent out his Venonat to battle, Ash Ketchum's comment was a bit cocky when he saw Koga's Venonat come out to battle as he had just defeated Aya's Venonat and he thought that Koga's Venonat would be an easy battle too. Koga realized that his Venonat was just about to evolve as it had been attaining points of experience and it evolved moments later into Koga's Venomoth. Ash Ketchum sent out his Pigeon and it had to be recalled pretty quickly as Koga's Venomoth used its Sleep Powder to put it to sleep. Ash Ketchum then sent out his Charmander to battle but that match-up also didn't last very long as Team Rocket interfered and the gym battle was interrupted.

Second Gym Battle Match against Ash

After dealing with Team Rocket, Ash's Charmander started a new battle for the gym badge against Koga's Golbat. This time Koga and Ash Ketchum decided to battle 1-on-1 for the badge. Ash's Charmander was able to endure Koga's Golbat Screech attack and then finished it off with a Fire Spin to give Ash Ketchum the victory and the badge.

Koga's Venomoth was offered up to trade by Koga as he was very impressed with Misty's Psyduck and he was almost willing to give it the Pink Badge for its help in dispensing Team Rocket. After his loss to Ash Ketchum, Koga realized that he was still far lacking in experience and he and his sister continued their training.