Harry comes to realize that Dumbledore knew that the Dursley's would abuse him, making him feel obligated to the Wizarding world to protect it, even with his life, Hermione believes he is right. So they, along with Sirius, Ginny, and Draco, try to leave the Wizarding world, unknowingly with Minerva's Support. They end up in the Pokémon world in the Alola region.

Harry: his Owl got turned into a Rowlet.
Hermione: her cat became a Litten.
Sirius: gets a Rockruff
Ginny: gets a Poplio
Draco: gets a Charmander