The latest issue of Televi-kun has revealed that Brock and Misty will appear in the September 14 and September 21 Pokemon Sun and Moon episodes, during which Ash will be journeying back to Kanto, and he’ll meet up with his old pals. They will be returning for only two episodes.
The official Twitter account for Pokemon Japan has also tweeted about the return of Ash’s original companions.
— ポケモン公式ツイッター (@Pokemon_cojp) August 29, 2017
Misty’s (Kasumi) voice actress Mayumi Iizuka also tweeted about her excitement about the happy news.
— 飯塚雅弓「Peace Ring」 (@MayuTama0103) August 29, 2017
Here are the character designs for the Pokemon Sun and Moon version of Brock and Misty: