Eden caught him as an Eevee while traveling in Johto and he became a major part of Eden's team. Umbreon as an Eevee rode on Eden's shoulder instead of in a Poke Ball. Like Ash's Pikachu, Eden's Umbreon hates riding in Poke Balls. In Eden's first episode, Eevee was captured by Team Rocket for Dr. Namba to use in his experiments. Eden came to rescue Eevee and was almost killed by Dr. Namba's machine while trying to save Eevee. Eevee saw what had happened to his trainer and was so angry that he evolved into Umbreon using his new move to save Eden and escape.
Umbreon is a very friendly Pokémon who cares for his trainer and other people. He hates it when people are in danger. He also hates Team Rocket because they almost killed him and his trainer.