The protagonist of Pokémon Ranger: Shadows of Almia is either a girl or a boy, depending on who you choose. Your character has traveled all the way from Fiore to attend Pokémon Ranger School in Almia.
Keith is a boy your age who is also aiming to become a Pokémon Ranger. At the start of the game, he comes off as cocky and unsensitive, and views you as a rival. However, after you compete with him and lose, you earn some respect from him and he decides to be friends with you. He accompanies you on the test of bravery, and is involved in the capture of the thief of the Stylers. Ms. April warned Keith that his refusal to depend on his friends would get him into serious trouble someday, but Keith wasn't listening, instead complaining under his breath about how the thief was released unpunished, not escaped like Ms. April had told Lamont.
He goes on the One-Day Internship with you to Vientown. He helps you capture the Tanglegrowth at the graduation ceremony, and then gets assigned to a base in Fiore. You read about his exploits in the newspaper as he begins to gain prestige. The next time you meet, his ego has cooled a bit, and he is quite startled and pleased to see you. He shows you his Partner Pokémon, Buizel. You get assigned the mission of going after Sven in the Chroma Ruins and investigating Team Dim Sun there. He goes after the Yellow Gem in Hippowdon Temple, but is captured and taken hostage by Heath.