FATE [BOOK 3 of The Bond Series]

After beating the Kalos league and moving on, Greninja decides to part off with Ash, after finding out Zygard needed Greninja's help. With Greninja gone, Ash feels like he should've regretted it but let's it go. And after 2 years of departure, Greninja finds there has been Pokémon all over the region getting attacked...