• English / United States: Sanpei
• Japanese / Japan: サンペイ
• Japanese (Romanized) / Japan: Sanpei
• Japanese (TL) / Japan: Sanpei

Sanpei is a ninja boy that knows the Ninja art of leaf concealment. He lives in the Ninja Village and likes to train alongside his Pokémon. He speaks in a pseudo-archaic manner. He has two brothers that live in the village: his eldest brother and strongest combatant of the ninja village, with his Gekkouga and the number two of the ninja village, his brother Nihei and Fushigibana.

Sanpei was watching Ash's Froakie train in a forest near Shoyo City when he revealed himself camouflaged in front of a tree. His training showed Ash Ketchum how helpful it could be when he defeated Ash's Froakie in a battle. Clemont commented that he'd never seen a Quick Attack like the one Sanpei's Frogadier was able to do. Sanpei is quite proud of the attack as no one gets up after the attack which is very fast and powerful. Despite being rivals on the battlefield, Sanpei was friendly enough to help Ash's Froakie learn Quick Attack at the request of Ash Ketchum although the training ended up that it learned Double Team.

After an encounter with Team Rocket, Sanpei gained new found respect for Ash Ketchum and the two of them vowed to have another battle if they met again.

Return to the Ninja Village

Sanpei was on his way home to the ninja village when he met Ash Ketchum and his friends in the area. He was heading home to participate in a festival and invited them to come along.

When Sanpei arrived, he was warmly greeted by his brothers and the villagers but they all wanted to see the results of his training.Nihei's Venusaur had a battle against Sanpei's Greninja right away. Nihei also said he wouldn't go easy on him.

Hanzo noted that Sanpei's Greninja fighting against Nihei's Venusaur meant that Sanpei had a disadvantage but nonetheless fought on an even level. Although, it wasn't enough to win the battle as Nihei's Venusaur was able to contain the damage to a minimum and waited for a chance to turn the tables.

When Hanzo was captured, Sanpei teamed up with Ash Ketchum to battle against Heidayu and together they were enough to hold him off while Ippei defeated Kagetomo to rescue Hanzo.