Yas

Yas is a character of the day who appeared in Showdown at Dark City. He is the Leader of the Yas Gym in Dark City.

The Yas Gym is in competition with the Kaz Gym to become the official Gym of Dark City so that he can earn money. After Ash refused to join his Gym, he tells his recruit to attack Ash with their Pokémon, in order to prevent him siding with the Kaz Gym against him. Later, the two Gyms rendezvous, and he sends his Scyther out again. During the fight of his Scyther against Kaz's Electabuzz, Ash, his friends, and a group of local children spill ketchup on him, Kaz, and Team Rocket. As both Scyther and Electabuzz have a strong aversion to the color red, these two battling Pokémon turned on their Trainers.

After their Pokémon run into each other, the two Leaders go after Ash, Misty, Brock, and the three kids who helped them. Pikachu then fends them off with a Thunder. When Nurse Joy, acting as an official of the Pokémon Inspection Agency, tells them that Ash, who is known by them as Tom Ato, will be their teacher, Ash tells them to restore the town, which they eventually do.

(Source: Bulbapedia)