Stephan challenged Ash to a Pokémon battle and chose Blitzle as his partner. Ash planned to battle him with Pikachu but ultimately chose Oshawott. The battle ended up being postponed because Oshawott lost his scalchop. Cilan politely asks Stephan to wait until the next day to have another battle with Ash. He agreed and said that he'd be training up in the mountains and to come and find him there when they were ready.
Ash and his friends found Stephan up in the mountains the next day, powering up his Blitzle using a bike-powered generator. Shortly after, he had his second battle with Ash. He ended up losing but was greatly impressed by Ash's skills. The two shook hands and he bid farewell.
In Reunion Battles In Nimbasa!, Stephan met up with Ash again in Nimbasa Town riding on his Zebstrika which had since evolved from Blitzle. He also entered the Club Battle tournament. In the next episode, he went up against Bianca who was his first opponent. Using his powerful Zebstrika, he managed to defeat Bianca's Minccino and advance to the next round.
Stephan battled Iris and her Emolga with his Sawk in The Club Battle Hearts of Fury: Emolga Versus Sawk!. Even with his special strategy of using Sawk's Close Combat to deflect Emolga's Attract, he still lost the battle and was knocked out of the tournament. In Club Battle Finale: A Hero's Outcome! he acted as a judge for Cilan and Burgundy's Connoisseur battle to see how well they could evaluate Ash and Iris's battle. At the end of the day of Ash and Iris's battle, he left Nimbasa Town with the other rivals.
Stephan reappeared in Climbing the Tower of Success! where he entered the Wishing Bell Festival contest with his Sawk. He passed through all of the portions of the contest, including one where he needed to cosplay as Nurse Joy. He, along with Ash and Ricky, was able to make it to the final portion of the contest where he was to climb Mistralton Tower while keeping his Litwick candle from burning out. The three made it to the top but Stephan and Ash were the last two after Ricky's candle was burned out by Pidove's Air Slash. Giving it all he had, Stephan crossed the finish line first and was declared the winner of the contest giving him the chance to ring the bell at the top of the tower.
It had turned out that the Litwick-shaped candle he carried was actually a real Litwick and was what helped him win as it blew out Ash's candle just before they crossed the finish line. Still, Miles declared him the winner and he was able to ring the bell. The wish he made was to win the Clubsplosion tournament and he then accompanied the group to Ambiga Town where they would all compete.
In The Clubsplosion Begins!, Stephan had entered Sawk in the Clubsplosion tournament and went up against Edmund, his first opponent. Though Edmund had a bit of an advantage because of the sudden rain and his Seismitoad's Swift Swim, Stephan was able to defeat him and advance to the second round. After the battle he was confronted by Montgomery, the winner of the last Clubsplosion, who had tried to convince him that his Sawk's strength could not compete with that of his Throh. Though insulted slightly, Stephan was interested in the prospect of gaining a new rival.
In Search for the Clubultimate!, Stephan offered to help Ash teach Scraggy how to make his Focus Blast more accurate by having him battle Sawk. However the training did not happen as Bianca interrupted wanting to poke Sawk's muscles again. In A Clubsplosion of Excitement! he attempted to help Ash again but were distracted from training when they heard crashing in the distance. There he saw Montgomery in the middle of a training session with Throh. He was undoubtedly impressed by Throh's power and wanted him to train with him and Ash but he refused. The next day, Stephan went against his second-round opponent, Cilan and his Pansage. Not even allowing the Connoisseur a chance to evaluate Sawk, Stephan took full control of the battle quickly and, literally, knocked his opponent out of the competition, advancing himself to the semi-final round. He discovered that his next opponent would be Bianca and defeated her again in Commanding the Clubsplosion Crown! which got him to the final round as did Montgomery.
Stephan and Montgomery
During lunch, Stephan and Sawk were given a special meal made by Cilan to help them in their battle. The others were worried for him feeling that Montgomery's Throh knew one other move that he didn't know about. Stephan only laughed knowing he would do well regardless because he had rung the Wishing Bell Festival. Once the battle began, Stephan did well in anticipating Throh's throwing moves and Sawk was able to parry them. However he did not expect his hidden move, Bind, leaving him to think of something quickly. He then thought of using Sawk's Bulk Up then Close Combat to escape which worked well. Near the end of the fray both Pokémon were at their limit and Stephan encouraged Sawk not to give up even when he was down. Just as Throh was about to grab Sawk again, he commanded one last Close Combat which finished off Throh and made himself the champion. After celebrating with Sawk, Montgomery approached him saying that he would win the next time they battled but congratulated him on the victory. The two shook hands and Stephan replied that he would win next time as well. Later on he said his goodbyes to the group and promised Ash a battle the next time they would meet.
He appeared again in Curtain Up, Unova League! revealing that he was going to enter the Vertress Conference. In the preliminaries he chose Zebstrika to battle against Radley and his Braviary and gained his first win.
Stephan appeared in Mission: Defeat Your Rival! and battled Ash in Strong Strategy Steals the Show!. He lost the battle and was eliminated from the competition. He stayed for the remainder of the league, watching all the other battles. He participated in the closing ceremonies of the Vertress Conference in A Unova League Evolution! and afterwards said farewell to Ash, his friends and Ash's other rivals.
Stephan appears prominently in the ending Let's Join Hands and makes a cameo appearance in the credits of Genesect and the Legend Awakened.
- J.P. Shibayama (Digimon)