Ash's Greninja finally reunites with Ash after completing its mission. Just then, Ash, Chloe and Gou are told by Professor Cerise to go to Kalos as he is suspecting something bad is going to happen there due to the fact that many wild Pokémon and domestic, have started Dynamaxing or Gigantamaxing randomly. Lysandre and Chairman Rose decide to team up to defeat Ash, and to bring back Eturnatus ( The darkest Day) and brainwash Zygarde again to take over the world. Will Ash, Chloe and Gou be able to stop them? ( I do not own any of the characters in this book, they belong to whoever made Pokémon )