Pokémon Black and White: Cheren is a childhood friend of the player who, like the player, lives in the starting town of Nuvema Town. While he holds a greater knowledge in Pokémon than his friends and tends to offer the player advice during the course of their journey, his comments are often witty and intellectual. He also misunderstands Bianca's humor often, to her dismay. Whilst Professor Juniper describes him as being very honest, she also remarks that he can be 'a little difficult'; his impatience in particular is often seen throughout the earlier stages of his journey. He is also described as being quite judgmental by Alder.
In keeping with the theme of truth and ideals often seen in Black and White, Cheren represents those who pursue ideals—more precisely, as N pointed out in Chargestone Cave, the ideal of strength. His goal is to become the Champion and he always strives to become stronger, yet the first time that Alder asked him why he strives to become stronger, he was quite unsure of his reasons. He then starts to ponder to himself how to do so—something that Alder said he used to do with his partner Pokémon as well—and what exactly it means to be strong. Alder also remarked that Cheren is a lot like Marshal.
Like the player and Bianca, Cheren receives a starter Pokémon as a gift from Professor Juniper 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. After the main storyline, Cheren can be found on Route 5. After talking to him there, he moves to Victory Road where he can be battled once a day.
Pokémon Black and White 2: In Black 2 and White 2, Cheren is the new Normal-type Gym Leader in Aspertia City, the player's hometown. He gives away the Basic Badge, replacing Lenora. Trainers who defeat Cheren will receive the Basic Badge, along with TM83 (Work Up). Outside of battle, Cheren works as a teacher at the Aspertia Trainer School, with one of his pupils being Lass Serena in the Aspertia Gym, according to her.
Cheren appears numerous times throughout the game, such as in Driftveil and Opelucid City, as well as Route 21. He gives the player and Hugh advice and guidance on the current situation, such as the freezing of Opelucid City, where Drayden learns of Cheren's ascension to the position of Aspertia Gym Leader.
After the player enters the Hall of Fame, Cheren can be found at Pinwheel Forest, investigating the activities of Team Plasma. He will accompany the player as a Multi Battle partner. After encountering Gorm, Cheren will thank the player with an Up-Grade and then return to the Aspertia Gym.
He can be called on the Xtransceiver to give the player advice on types and Abilities.
In the anime: Cheren was mentioned by Professor Juniper in New Places... Familiar Faces!, where she explained that he was a new Gym Leader located at Aspertia City. Cheren first appeared in There's a New Gym Leader in Town!. Ash and his friends met him at the Aspertia Gym, where they learned that he was also a teacher at the Trainers' School, which was located at the Gym. When Pikachu and Axew accidentally caused loud noises on the School's PA, making all the School's Pokémon run wildly around, Ash, Iris, and Cilan helped Cheren to gather them.
Finally, only a Shinx was left. When it was too scared to come closer, Cheren went to it, and, ignoring its Electric shocks, managed to calm it down. Afterwards, Cheren agreed to have an unofficial battle with Ash. Ash used his Oshawott, while Cheren used his Herdier. Cheren eventually won the battle, with Herdier taking Oshawott out with a super effective Thunder Fang.
Cheren made a cameo appearance in the ending credits of Genesect and the Legend Awakened.
In the manga: Cheren is friends with both Monta and Bianca, he is very knowledgeable about Pokémon, which Monta dislikes. Anywhere Monta slips up he won't hesitate to tell him the right way.
He first appears with Bianca when Monta is attempting to capture a wild Patrat and Watchog. Monta is just about to capture the Watchog which Cheren tells him that it is not the right way. He explains to Monta to remember that when two Pokémon come out at the same time, one should knock out the one they don't want before they can get the one that they do want. Cheren suddenly decides for all of them to take their Pokémon journey together, which a man on his bike overhears. He starts insulting them making him and Monta angry.
He uses Tepig in a Double Battle with Monta's Snivy against a Biker King's Braviary, it looks like they were about to lose, but they uses a combination attack which Cheren thinks of, fainting Braviary. Cheren battles Monta in The Key to Triple Battles using his Tepig, Pansage and Basculin against Monta's Snivy, Panpour and Roggenrola. 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. He has traveled with Monta and Bianca from time to time.
Cheren battles Monta in The Birth of the Best Pokémon Trainer! in a Single and Triple Battle. Even though the Single Battle was easier for Monta, Cheren gave him a hard time in the Triple Battle.