• English / United States: Rainer
• Japanese / Japan: ミズキ
• Japanese (Romanized) / Japan: Mizuki
• Japanese (TL) / Japan: Mizuki

Rainer is one of Mikey's older brothers. Together with his brothers, Sparky and Pyro, they run Evolution Garden Parties at Number 14, District 3 in Stone Town. He wanted Mikey's Eevee to be the main event in their party so he could show the other people the charm of evolution. Rainer likes Vaporeon out of the Eevee evolutions and fashions his hair similar to the look of a Vaporeon.

After his debut battle as an Eevee Trainer against Team Rocket which he won, Mikey showed his brothers that he was strong with his Eevee even without it being evolved. Rainer was amazed that he won his first battle and apologized and stated he was wrong about what he said earlier.