There's a New Gym Leader in Town! - S16.E14

The group's boat arrives in Aspertia City, and they arrange to meet Cheren, Professor Juniper's acquaintance and the city's new Gym Leader. A teacher at the local Pokémon School, Cheren is lacking in confidence regarding his worth for the title, something Cilan - as a former Gym Leader himself - connects with him over. After misadventures in the Pokémon House on the school grounds - including a series of mishaps between Cilan, Pansage, and a flock of Ducklett - Ash has an unofficial Gym match against Cheren, Oshawott facing off against Herdier.