The most recent episode of the anime to air in Japan showcased Ash's victory over the incredibly powerful Gym Leader of Hammerlocke City, Raihan, which pushed him into the position of 8th-best Trainer, and to the Masters Eight, a group comprised "of the eight best Pokémon Trainers in the world", which "consists of Elite Trainers who have won other championships and competitions around the world."
The rankings for the Masters Eight are as follows:
In addition to the other Champions of the regions, some of Ash's most fierce companions and rivals, who he's had many fiery battles with, will compete in the tournament. Ash's former traveling partner Iris, who is now the Champion of Unova, will compete at Rank 7. Ash's rival, who defeated him in the Kalos League finals, Alain, is in the tournament at Rank 6 as well.
The Pokémon anime currently airs every Friday from 6:55 PM JST on TV Tokyo.