Cheren was friends with Black and Bianca by five years old. He was very observant, realizing that though Black had told Bianca's dad he'd give up battling right now for Bianca's sake, Black had not given up on battling in general. Cheren saw that Black was studying battle.
He seemed to have gone along with it, helping Black carry books in the library. He also read about the Pokémon League himself, listening to Black's plans seriously.However, he was more reasonable than Black, realizing that at their age, they weren't fit for traveling Unova. He tried to calm Black down but failed, resulting in Black's mental breakdown as his brain overloaded from his dreams. When Bianca irritated a wild Rufflet, Cheren tried to snap Black out of it. Cheren then ran to help Bianca, and a certain wild Munna attached himself to Black's head.
Years later, he convinced Professor Juniper to give Black a pokédex.
Expecting to receive a Pokémon from Professor Juniper, Cheren and Bianca go looking for her when none shows up. The three find out that Black opened the box without them and vanished, leaving destruction and an unconscious Snivy and Oshawott behind. Bianca immediately hands the Snivy to Cheren, declaring that it looks like him.
The three go to look for Black, Cheren enduring Juniper's reprimands about Black's irresponsibility. He convinces her again to give Black a chance.
He and Bianca figure out that their pokédexes don't work due to water damage.
He and Bianca go to Juniper's house with her, and while Juniper is trying to fix their pokédexes, Bianca gets impatient and has a battle with Cheren in the living room. During the battle, Snivy's Tackle throws Oshawott into Bianca's face, making her cry and have a tantrum. She runs around whacking him while her Oshawott does the same to his Snivy. Professor Juniper intervenes, and Cheren quickly apologizes for making a mess, trying to get Bianca to apologize too. He goes on to explain the history behind Black's desire to go on a journey to Professor Juniper and offers to go tell Black to be careful with his pokédex.
Cheren intends to go find Black, but waits instead for Bianca.
They catch up to Black in Striaton City, where they find Black having lunch with a girl. Bianca immediately thinks Black is having a date, but Cheren is more observant and comments that it doesn't seem like a date. The three end up challenging the three gym leaders to a triple battle. Cheren's Snivy is knocked out by Chili's Pansear, but is revived at the end by a clever use of Cilan's Pansage's leaves. Cheren obtains the Trio Badge.
After the battle, Cheren stays behind to thank the gym leaders for the battle and to apologize for something; Bianca waits for him to finish before they go to meet up with Black in western Striaton City, where Black gives them each an Xtransceiver to stay in touch with him. They also meet White, who comes for Black.
After Black and White leave, Bianca realizes that Black forgot to give them his Xtransceiver number. Cheren hurriedly takes off to continue following Black with Bianca.
Cheren trains his team of Pokémon diligently but without any real intent to enter the Pokémon League. He is delighted when his Pidove evolves into Tranquil while training in Driftveil City. Soonafter, he encounters Black and takes him to train at the move tutor's, where Cheren's Snivy learns Grass Oath. However, Team Plasma interrupts their training by attempting to kidnap Cheren's Pokémon, prompting both boys to chase them into the Cold Storage. Cheren and Black defeat the grunts by combining Grass Oath and Fire Oath. Plasma Sage Zinzolin and his followers retreat. Cheren and Black then part ways.Aspertia City's trainers' school. Among his students are Petashi, Hugh, Rakutsu, and, most recently, Faitsu. Cheren decides to hold a tournament for his students; the two winners would receive pokédexes from Bianca. Rakutsu and Faitsu win, but Faitsu has to be coaxed into accepting her reward.
Even as a child, Cheren was observant and sensible. He could see clearly with logic as Black was overwhelmed with passion. However, Cheren is far from cold; he is emotional, shouting, clinging to Black's arm, and begging him not to rush recklessly off to Professor Cedric Juniper's lab.
He is extremely polite and well-mannered.