Oba

In Pokémon Diamond, Pearl, and Platinum, Flint is the third member of the Sinnoh Elite Four. He is friends with Volkner, the Gym Leader of Sunyshore City. Flint’s younger brother is Buck. His grandfather runs the Battleground.

Flint first encounters the player in Sunyshore City, informing him about the recent blackouts and Volkner’s disillusionment as a Gym Leader. He asks the player to bring back the excitement of Pokémon battles to Volkner before seemingly returning to the Pokémon League.

In Pokémon Platinum, Flint and Volkner challenge the player and their rival to a double battle upon their arrival to the new Battle Frontier (Wiki).