He appeared in episodes 51 and 52 (Inuyasha's Devoured Soul and The Demon's True Nature). He is a large moth yōkai and calls Inuyasha "little man".
He covets Tetsusaiga when he sees Inuyasha wielding it, claiming it was a "mighty sharp sword". Quickly sealing Miroku and Inuyasha in his poison cocoon, he tries to wield Tetsusaiga, but he could not wield it, seeing as he was a demon. Growing bored, the leader taunts Inuyasha by eating some women. Inuyasha had endured enough abuse, so when Kagome and the rest of the gang appear he transforms into his yokai form. Gatenmaru scoffs, and transforms into his true form, a giant blue moth demon, but he underestimates Inuyasha and is quickly ripped apart. Inuyasha then massacres Gatenmaru's bandits.
Gatenmaru's name means "Moth God Demon".
Inuyasha also later faces Gatenmaru's brother, Gamamaru, who instead of using poison cocoons as an attack, instead encases the victims and attacks them in their dreams.
Attacks and abilitiesEdit
Poison Cocoon: Produces a large quantity of coccon that melts flesh.
Dust Tornado: Appears in the anime only. Gatenmaru flaps his wings to create a large twister.
Giant Broad Axe: Only in human form. He wields it against Inuyasha for a brief period when they first duel.