Sennin

was a hermit and the former master of Tōkajin.

History
He took in Tōkajin and trained him to become a sage. Tōkajin grew frustrated after a couple of years of training due to the amount of time it took for him to become a sage. He decided to turn against his master. His body was eaten by Tōkagin, but he was alive in the form of a plant because he did not reveal all the secrets to create the potion for eternal life.

During the story
Inuyasha, Kagome Higurashi, Miroku, and Shippō were trying to escape Tōkajin's temple. He asked is someone was there after hearing Inuyasha and Kagome argue about how to escape from the temple. He told them that he was once Tōkajin's master. Inuyasha grabbed him by the stem and angrily asked how he could train such a monster to become a sage. The sage explained that Tōkajin turned against him and is no longer a human.

Tōkajin soon arrived explained that reason he kept him alive was to learn the potion of enteral life from him. An already injured Inuyasha tried to take the shards of Shikon Jewel shards from Tōkajin's bellybutton, but he was knocked back into a vat of human-faced fruit. The sage told Inuyasha to drink some of the potion that was in the vat. It was an imitation of eternal life potion that Tōkajin made, but it was effective enough to heal flesh wounds. Inuyasha refused to drink it and claimed that he could beat Tōkajin without drinking something so disgusting.

Tōkajin easily subdued Inuyasha. Kagome grabbed a nearby bow and arrow to save Inuyasha. The sage told her that a bow and arrow couldn't bring down Tōkajin. As she was prepared to shoot, the sage could sense Kagome's spiritual power that surrounded the bow and arrow. The bow suddenly broke before she could shoot. He pleaded with Kagome to slay Tōkajin and used the last of his energy to change into a bow and arrow as a way to make amends for training him in the first place. Kagome was able to remove the jewel shards from Tōkajin. The bow disappeared afterwords.

Personality
He was a very knowledgeable person. He was the only one who knew the potion for eternal life. He felt great shame for taking on Tōkajin as his student due how he was abusing his teachings for evil purposes.

Powers & Abilities
As a sage, he has great spiritual power and knows many spells. He is the only one who knows how to make the potion for eternal life. He is able to sense Kagome's spiritual power and use the last of his power to transform himself into a bow and arrow to defeat his former apprentice.

Manga vs. Anime

 * The manga shows what Tōkajin did to his body. It was hacked with an axe, and then devoured.
 * In the manga, he is kept inside the lowest chambers of the temple. In the anime, he is kept outside beside Ninmenka.
 * In the manga, Tōkajin turns against him of his own accord. in the anime, Tōkajin turns against him after being influenced by Ninmenka. Furthermore, in the anime, Tōkajin turns him into a flower was so he could be used as fertilizer for Ninmenka.

Trivia

 * His seiyū, Tamio Ōki, also voiced Sugawara no Michizane from Rumiko Takahashi's previous series .

Media appearances
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Manga

 * Chapter 83
 * Chapter 84

Anime
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 * Episode 58

Tōkajins Meister maestro de Tokajin 仙人