Manta is the first friend of Yoh Asakura, he can see spirits but lacks shamanic power for much of the anime and all of the manga.
While coming home late from school one night Manta decided to take a shortcut through the graveyard. When passing through the cemetery, he bumps into Yoh Asakura who says hello and reveals his ghost friends which Manta can see. The next day, Yoh joins Manta's school and becomes friends with him. During the shaman king preliminaries and journey to America, Manta accompanies Yoh on all of his adventures throughout Tokyo, but when Yoh leaves tokyo during a Shaman fight, Manta stays behind with Anna. During the first event of the tournament, Manta watches Yoh and his friends fight in teams of three against other shamans.
Manta Oyamada, who is created by Hiroyuki Takei, has no current information on what inspires the author to create him. He first appears in shaman king volume 1 and episode 1. His Japanese actress is Inuko Inuyama, and his English actor is Oliver Wyman.
"And so... Yoh's quest to be the shaman king came to an end. But life goes on. The contestants of the shaman fight carry their hopes and dreams into battle. There are losts of people in the world...and they all have their own unique aspirations. The dreams of some clash with the dreams of others. There will be laughter and tears. How many of us..will make our dreams come true? And how many of those realized dreams... will actually bring us happi-ness? No one knows...the answers to those questions."
Manta -Vol. 19 - Narration at the end of prologue chapter where Yoh drops out of shaman tournament
Manta's life is change when Yoh opens his eyes to the shaman world. As he witness Yoh's dreams and the dreams of shamans clash in the shaman king tournament, Manta wishes he was in their shoes. After the shaman king tournament is over, Manta takes control of his father's electronics company and research how to apply shamanic powers to help the real world.
NOTE: These are not official arc names due to the lack of information from the author and notes in the manga.
NOTE: The information below is manga only info. See anime differences under "anime and manga differences" paragraph.
Manta's role, during the shaman king preliminary matches, is watching Yoh and supporting him when Yoh trains and fights. Sometimes, he helps research the enemies for Yoh.
Manta's adventures let him to encounter Amidamaru, a Japanese samurai, and Bokuto no Ryu. Manta observes the powers of a shaman up close when he sees Yoh easily defeats Ryu and his gang. Another time that Yoh fights is with Ren Tao, Manta watches Yoh fights Ren and Yoh's miraculous victory over the Chinese shaman and his spirit alley, Bason. At the hospital, Manta and Amidamaru wait for Yoh to wake up, but Anna barges. Manta, who is shocked, learns that Yoh and Anna are engage at a young age. During the training period for Yoh, Manta and Yoh encounter Ren's sister, Jun Tao, and her jiang-si, Bailong. Manta is a fan of the martial arts and his role model is Li Bailong. He assists Yoh and Anna when Yoh needs an object like a sword with a proper handle. He steals Ryu's bokken and throws to Yoh which Yoh frees Bailong from Jun's control. When Anna needs a name for Li's master, Manta quickly responds.
The only time when Manta is in danger, is the second preliminary match of Yoh versus Faust the VIII, a German necromancer. After Faust pins down Yoh, he proceeds to dissect Manta by opening his body cavity up. This inhuman act infuriates Yoh and forces Yoh to waste his furyoko (or mana) before the official fight begins. During the battle, Manta witness Yoh's success in destroying Eliza's leg bones, but Yoh lost the match due to his oversoul disappearing entirely. Faust, who is enraged at Yoh for calling his Eliza a doll, attacks Yoh with a 20 ton calcium giant skeleton, but Ren appears out of nowhere and destroys Faust's oversoul.
Manta, who is at the hospital, receives bad news from his family and his friend, Yoh. When Manta's mother asks Manta why he is injured, Manta refuses to answer her. Manta's young sister teases Manta, but when Manta's father arrives, he tells Manta what he knows about Yoh Asakura. After Manta's father warns Manta not to go near Yoh, Manta protests, so Manta's father slaps him. Manta's father tells Manta to come back to America. After his family's visit, Manta heads to Yoh's room which is in the same hospital. Yoh lies to Manta by telling him it was his fault that cause Yoh's defeat. Yoh tells Manta to stay away from the shaman fight. Unknown to Manta, Yoh lies to protect Manta.
At the airport, Manta meets Ryu, who wants to go to America to become a sushi chef, and Ryu's influence makes Manta change his decision which is to follow Yoh. During the road trip to Izumo, Manta and Ryu talk about dreams and other facts like when Ryu reveals his fondness of souvenir shops to Manta. After arriving to Izumo, Manta and Ryu are attack by Tamao's spirits, Ponchi and Conchi. When Tamao makes an appearance, Ryu asks her to go out with her, but Ponchi and Conchi cut off his coif and hit Ryu's groin. Then Ponchi uses his belly to trap Manta while Tamao uses Conchi as a oversoul arrow. However, Anna stops Tamao from hurting Manta, and she forces Tamao's spirits to confess that they lie to Tamao. After Ponchi and Conchi reports that Yoh's coming home from his training, Manta and everyone greet Yoh who comes out from the cave of Yomi. Manta witness Yoh's evolved oversoul when Yohmei Asakura tests him with his leaf shikigamis.
Manta watches Ren and Yoh's battle. After Yoh successively makes Ren waste his mana in anger, Yoh meets Ren head on by enlarging their oversouls. The results of the match is a draw between the two shamans. As soon as Goldva finishes announcing the next part of tournament which is in America, Yoh's house becomes festive when Ren, Horohoro, Pirika, Tamao, Anna, Yoh, and Manta with their respective spirits have dinner and a relaxing bath.
When Bason asks for Yoh's help to save Ren who is held captive by Tao Yuan, Manta accompanies Yoh, Ryu, and Horohoro to China. During the Curse Squad attack on Yoh and friends, Manta informs Yoh and Ren that the leader is Sha Wen whose soul is place into a genetically modified corpse. After Jun Tao has Bailong destroy Sha Wen's body, Manta and the rest of the shamans arrive to Tao Yuan's room. Manta witness how Ren defeats his father's oversoul and Ren's grandfather and mother tells Tao Yuan to stop. After Manta and friends get invited to dinner, Manta questions why Ren's grandfather commit evil deeds. Ren's grandfather replies that the line of evil and good are blurry due to an everchanging world and he did these deeds so their family can survive from their persecution.
Manta only appears with Anna, Tamao, and Mikihisa after Yoh and his team arrives in Patch village, and Manta sees Faust, Hao Asakura with his followers and the Great Spirit. This is the first time Manta sees Hao Asakura and he and his butler, Tamurazaki, watch Anna and Hao share their conversation. Manta witness Hao grabbing Anna's right hand and comments on how she is the ideal bride of a shaman king. Anna slaps Hao with her left hand, and tells Manta and Tamao to go in the cave immediately. After Ponchi and Conchi harass Manta and Tamao to make a move on each other, Manta quickly leaves the house to a river. While thinking about the Great Spirit and Mikihisa, Manta stumbles upon Faust who is singing about his "Faust Love." When Yoh and Anna arrives, Manta is sitting in Faust's lap. Faust asks Yoh if he can join their team, and Ryu, who comes out of nowhere, informs Faust that their slots are full due to Lyserg. Faust, who looks sad, wheels away and he takes Manta with him. At the diner, Manta tells Yoh that he sympathizes with Faust because Faust, who is obsessed with medicine and his love for Eliza, turns to necromancy. Then Anna gives Yoh advice that having Faust is beneficial because he is doctor.
Manta witnesses the massacres of shaman teams when he sees how the X-Laws and Hao Asakura's fight. After Ren's team won the first match of the tournament by defeating Team Tsuchi Gumi (English: Earth), the second match is X-I ( Lyserg's team) versus Team Nile. After Lyserg's spirit, Morphea, refuses to kill Anatel, Iron Maiden Jeanne steps in and murders Anatel first then Nakht and Khafre second. Manta faints from the blood shed which Iron Maiden Jeanne claims it is justice. After Team Hana/ (English: Flower) defeats their opponents, Manta watches Hao's team Hoshi (English: Star) fight with Team X-III. Manta refuses to watch and goes to call the police because Hao kills Meene Montgomery first and Cebin Mendel. After Amidamaru fails to stop Manta from leaving, Iron Maiden Jeanne makes her statement which stops Manta from running away.
Manta's name is change to Morty in the dub for unknown reasons. An interesting note, "Morty" is a pun on the latin prefix of death.
Note: In the anime, characters meet characters early or later their original manga counterparts.
Unlike the anime, Manta meets Horohoro unconscious on a road, and Yoh and Manta brings Horohoro to their house. Manta, Ryu, and Yoh ask what is Horohoro doing. When Yoh lets Horohoro stay at his house, Anna forces Horohoro to do chores if he wants to stay at Yoh's house. (see episode 9 and volume 4 for comparison)
Manta can use an oversoul with Mosuke by using his laptop as a medium. By demonstrating this ability, he would be considered a shaman in the anime only.