Urayama

Urayama is the owner of the Pokémon Mansion and Trophy Garden. He is also said to be the owner of Amity Square. His house has a back garden where players can capture wild Pokémon.

He is apparently a compulsive liar, as he will repeatedly insist that a Pokémon appears in his garden despite not even residing in his region. His butler, who serves him well, covers up for his lies, importing said Pokémon into the garden and allowing the player to capture rare Pokémon not found elsewhere in Sinnoh. This is often very helpful in completing the National Pokédex.

(Source: Bulbapedia)