Pokemon Crystal: Raikou, the Legend of Thunder!

Animation - 2001

Kenta, a Pokemon master in the making, meets up with his childhood friend, Marina, at a Pokemon Center, to see how their skills have developed. Their battle is interrupted by a thunderstorm and the arrival of Bashou and Buson, two Rocket-dan members using the Crystal System (which attracts Electric-type Pokemon). Their ultimate goal is to, under the guidance of professor Shiranui, bring Pokemon back to Sakaki. Kenta and Marina stumble upon this plan, and they try to stop it, but things get more difficult when the legendary Pokemon Raikou is captured.