Manta Oyamada is an intelligent but worrisome teen who always carries a "dictionary/encyclopedia/compendium of all human knowledge." He has a sixth sense, meaning he can see supernatural beings, even though he is not a Shaman. He is very expressive and a bit panicky. His rather abnormal height has gotten him into trouble numerous times, once having been mistaken for one of the shy nature spirits, and being cut open and used as a hostage of sorts during You Asakura's match with Faust VIII.
In the anime, during the final battle with Hao, he actually becomes a Shaman and is able to merge with a spirit. His weapon is a hammer, and his unofficial guardian ghost is Mosuke, the best friend of Amidamaru who forged his sword, the Harusame. After that episode in the anime, Manta is able to junction spirits to his laptop.
Manta Oyamada narrates the story in the manga and anime, allowing readers and watchers to understand the plot more efficiently. He is referred to as "Morty" (short for Mortimer) in the English anime. (Hiroyuki Takei mentioned Manta's character was modeled after Japanese pop singer T.M.Revolution in an interview published in the March 2004 English language issue of Shounen Jump.)
