Bel is a childhood friend of the player. Though she is somewhat unreliable and a bit of an airhead, she also has a strong side, as shown when embarks on a Pokémon journey despite her father's strong opposition.
Like the player and Cheren, Bel receives a starter Pokémon as a gift from Professor Araragi at the start of the game; she chooses the Pokémon with a type disadvantage to the player's starter. The player will encounter and battle her several times throughout the game.
Although Bel has yet to appear in the actual chapters, Bel was seen in a preview pic for the B/W arc of Pokemon Adventures, alongside Cheren, the player characters' counterparts, the three starters, N, and Professor Araragi.
In the Pokémon Master Black & White manga
Bel is a friend of both Monta and Cheren, not much is known about her, but although she is not as knowledgeable as Cheren. Her starter Pokémon was Mijumaru at a type disadvantage to Monta's Tsutarja. She first appeared with Cheren, and after Cheren's lecture telling Monta his is inexperienced, Bel says he said too much. She then watches Monta and Cheren battle the Bike Gang King.