Empoleon lost his vision while protecting Galyous from some wild Pokémon. He is very important to Galyous and they never left each others side ever since Empoleon was a little Piplup.
They are best of friends, they share their victories and their losses.

Man, I really love Empoleon, he is my favorite Pokémon, his design is so majestic. It's hard to believe a Piplup evolves to something like this...

Galyous Starkk (c) FlyAwayGrenade / ImpactAlchemist (DA)