Calem is a boy living in Vaniville Town with his friends Tierno, Trevor, and Shauna. He recently moved into Vaniville Town. His mom owns a Rhyhorn and Fletchling, the latter of which wakes Calem up at the start of the game.
As a non-playable character
Calem is a young boy who lives in Vaniville Town when the protagonist moves into town. Calem is the main rival of the character, choosing the starter Pokémon which is super effective to the player's. He is also the character who teaches the player and Shauna how to catch a Pokémon, catching a Bunnelby with the use of his Fletchling. Soon after, he can be seen in Santalune Forest with the other friends.
Calem is the child of two prominent Pokémon battlers, and is seen as one of the two best battlers of the group of friends, alongside the protagonist.
Pokémon
Capture tutorial
Calem has another Pokémon besides his Fletchling, likely his starter, as noted by having two party slots filled during the tutorial.