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.