Manta Oyamada is a clever yet anxious teenager who constantly carries a "dictionary/encyclopedia/compendium of all human knowledge." He possesses a sixth sense, enabling him to see supernatural beings despite not being a Shaman. Manta is highly expressive and tends to be somewhat panicky. His unusually short stature has caused him trouble on multiple occasions, including being mistaken for a nature spirit and even being used as a hostage during You Asakura's match with Faust VIII.
In the anime, during the final battle against Hao, Manta becomes a Shaman himself and merges with a spirit. His weapon of choice is a hammer, and his unofficial guardian ghost is Mosuke, the best friend of Amidamaru who forged the sword Harusame. Following this episode in the anime, Manta gains the ability to connect spirits to his laptop.
Manta Oyamada narrates the story in both the manga and anime, helping readers and viewers better understand the plot. In the English version of the anime, he is referred to as "Morty" (short for Mortimer). According to an interview in the March 2004 issue of Shounen Jump, Hiroyuki Takei mentioned that Manta's character was inspired by Japanese pop singer T.M.Revolution.
