Illoo has an elderly appearance with a brown skin, long eyebrows, and a thin, long beard. He wears a light brown colored kimono and above that a gray colored robe with yellow linings and a prominent hat-like section in the superior part. He also wears a collar of khaki-colored beads and a red charm in the center and carries a small wooden staff on his right hand.
Illoo first appear in EP005, in which he makes illusions of some girls to make Bear and Eddie believe they are receiving chocolate for Valentine's Day. Nate soon realizes he is the only one not to receive chocolate and demands Illoo for that. Nate summons Jibanyan, but Illoo causes the cat Yo-kai to believe in eating chocolate bars, which actually was a playground structure. Nate then summons Manjimutt, but he also falls into the illusion into receiving chocolate from a lot of girls. Nate then resorts to defeating Illoo himself with a "Fire-Nate-Tornado" illusion of his, which works enough to have Illoo giving him his Yo-kai Medal, but not without Nate falling into an illusion of Katie giving him chocolate as well.
He is first summoned in EP008 and creates an illusion of urinals in the hallway at the time when the students were inspirited by Fidgephant.
In EP027, Illoo was seen in Yo-kai-lifornia where he was among the Yo-kai waiting in line for the release of the Yo-kai Watch Model Zero.
In EP039, he defeats Failian by creating an illusion of him leaving Earth with some aliens.