From Bulbapedia, the community-driven Pokémon encyclopedia.
Ishihara (Japanese: Ｍｒ．イシハラ Mr. Ishihara) is a Pokémon card collector. He is named and modeled after producer Tsunekazu Ishihara.
Ishihara owns over 10,000 cards. He's also written many books about the Pokémon Trading Card Game.
In Pokémon Trading Card Game, Ishihara can always be found in his house on the cape to the northwest after being told by someone in the game where he is. He will trade very rare promotional Pikachu cards to the player for rare colorless cards. In order, he will trade a Surfing Pikachu for a Clefable, a Flying Pikachu for a Ditto, and an alternate design Surfing Pikachu for a Chansey. After all three trades have been completed, Ishihara will leave in search of someone who will give him the Phantom Cards.
In Pokémon Card GB2: Here Comes Team GR!, Ishihara moves between his house and a new area, his villa. He will still trade cards with the player, but this time, he will be available to duel in his villa after all his trades are completed. He uses the Very Rare Card Deck, which contains many rare promotional cards.