Cheren Is One of your firends from childhood, He lives in the same small town as you do and receives his starter pokemon at the same time as you. He battles you reguarly to test how your battling skills have progressed. He will pick the starter pokemon that has the advantage on you.
Bianca is another one of your childhood friends, she arrives late to your house on the day of getting your starter pokemon. She will battle you as well thorugh your journey across the Unova region. However, she picks the starter pokemon that you have the advantage over.
Juniper is the professor of the Unova region, unlike the other professors, the professor is female this time. She gives you and your friends your starter pokemon along with a pokedex, she encounters you many times during your journey both in person and through the Live caster.
Makomo is a friend of the professors, she helps you along with your journe, she's a researcher and is very much involved with the global link system. She gives you the C-gear item.
N is a very mysterious trainer, he battles you many times throughout your journey, he has a dark secret though, which he reveals to you, he's the leader of theevil organisation. team plasma. He's got a strong opinion that humans should not have pokemon as slaves.