Cheren is a childhood friend of the player who, like the player, lives in the starting town of Kanoko Town. He is an intelligent boy knowledgeable in Pokémon, and will as such offer the player advice during the course of their journey. His goal is to to become the Champion.
Like the player and Bel, Cheren receives a starter Pokémon as a gift from Professor Araragi at the start of the game. He always chooses the starter with a type advantage over the player's starter. The player will encounter and battle him several times throughout the game.
Cheren makes an appearance as one of the Pokédex holders of the Unova region, he is a good friend of Black and along with Bel, recommended him to be the third Pokédex holder for Professor Araragi. Due to an accident, his and Bel's Pokédexes are currently broken, leaving Black with the only working one. Strangely, in Pokémon Adventures, his starter is actually weak to that of the protagonist which is unlike the games, where it is stronger than the player character's.
Snivy was first seen in Professor Araragi's lab where after getting berry juice sprayed on it by Araragi's Tepig, began fighting with it only to be stopped by Oshawott. It later appeared in Kanoko Town where it was delivered to Black along with Tepig and Oshawott and once again fought with Tepig and was once again stopped by Oshawott. Later Bel picked Snivy up and immediatly gave it to Cheren, without giving either of them a chance to protest.
In the Pokémon Master Black & White manga
Cheren is friends with both Monta and Bel, he is very knowledgable about Pokémon, which Monta dislikes. Anywhere Monta slips up he won't hesitate to tell him the right way. He first appears with Bel when Monta is attempting to capture a wildMinezumi and Miruhoggu. Monta is just about to capture the Miruhoggu which Cheren tells him that it is not the right way. He explains to Monta to remember that when two pokemon come out at the same time, you have to knock out the one you don't want first before you can get the one that you do want. Cheren suddenly decides for all of them to take their Pokémon journey together, which a man on his bike overhears. He starts insult them making him and Monta angry.
He uses Tepig in a double battle with Monta's Snivy against a Bike Gang King's Wargle, it looks like they were about to lose, but they uses a combination attack which Cheren thinks of, fainting Wargle. Cheren battles Monta in PBW02 using his Tepig, Yanappu and Basslao against Monta's Snivy, Hiyappu and Dangoro. He starts off with a lecture about triple battles. With his great knowledge of triple battles he gives Monta a hard time, but is eventually defeated.
Cheren's Tepig is well trained and has a type advantage over Monta's Snivy. It was first used in a Double battle with Snivy against the Bike Gang King's Wargle. After Snivy tries a Vine Whip which hardly does any damage, he goes in for a fire attack which hardly does any damage too. Tepig is then sent flying with Peck. It goes in with a Fire Oath with Grass Oath creating the combination needed to defeat Wargle.
It battles Monta in PBW02 with Yanappu and Basslao against Monta's Snivy, Hiyappu and Dangoro. It starts off with an Ember on Snivy, before taking a hit for Basslao by switching places with it, not hurting it much. But seconds later, Hiyappu uses Surf fainting it.
Cheren's Basslao was first seen in a battle against Monta's Snivy, Hiyappu and Dangoro with Tepig and Hiyappu. It is about to get hit by Snivy's Vine Whip but switches places with Tepig. It then gets hit by Hiyappu's Surf which does not do much damage. But along with Yanappu is defeated by a powerful Rock Slide from Dangoro, fainting it.