Ash in “Catching the Aura of Fate!”

[about Greninja] When I came to Kalos, Froakie was the first Pokémon I caught. On our journey, we got stronger and stronger. One time, we had a fight because I tried too hard to win a battle...but we made up. Eventually, we took part in the Kalos League and after that, Greninja wanted to protect Kalos, so it stayed behind. [Nice story, but why did the writers ignore the Ash-Greninja form? Also, Zygarde appears to be written out of this series due to irrelevance. Also, no mention of Team Flare?]