Ep. 19: Ash prepares for a rematch against Tapu Koko with help from Sophocles' scientific methods.
Aired on March 23, 2017

19
Ash starts training to face Tapu Koko in a potential rematch. Sophocles assists by applying scientific techniques to the practice sessions, which produce unexpected outcomes. These surprising results catch the attention of Tapu Koko, who becomes interested in their progress. Consequently, Tapu Koko issues a challenge to Ash and Pikachu. The confrontation takes place with the entire Pokémon school watching the event unfold. The episode focuses on the preparation methods and the subsequent public challenge issued by the guardian deity.
Episodes
- Ep. 15 · Rockruff trains at a secret site to overcome its fear and defeat Magmar
- Ep. 16 · Popplio and Rowlet drift into Team Rocket's base after a training accident.
- Ep. 17 · Rotom and Pikachu investigate the disappearance of Ash's Electrium Z-crystal
- Ep. 18 · Mallow seeks rare Yellow Nectar for stew while Ash helps and Team Rocket interferes
- Ep. 19 · Ash prepares for a rematch against Tapu Koko with help from Sophocles' scientific methods.
- Ep. 20 · Ash and Pikachu kayak to Treasure Island and rescue a trapped Wimpod with help from local Pokémon.
- Ep. 21 · Ash and Pikachu encounter Litten and the aging Stoutland, leading to a poignant farewell and a new bond.
- Ep. 22 · Ash and Litten are swallowed by Palossand after a shovel incident
- Ep. 23 · Ash and classmates meet DJ Leo and his quarreling Alolan Dugtrio while Team Rocket attempts a theft.