Oyamada Mansumi

Oyamada Mansumi (小山田萬純) is a fictional character in the Shaman King series. He is the president of large corporation and the husband of Oyamada Keiko and father of Manta and Mannoko.

Personality
He is a strict father who believes that parents must protect their children at any cost. He is not above hitting his own son when he talks back to him, and is also prepared to force him to back come back to America. But he still has high expectations of him and wants his son Manta to inherit his company. He is however a bit of a romanticist and wishes to expand his company into outer space.

Shaman Fights in Tokyo
Midori drives Mansumi to the hospital where his son Manta is recovering. When Mansumi asks if his son has learned his lesson, Midori tells him that Manta refuses to transfer schools because the boy is too focused on his best friend, Asakura Yoh. Upon realizing this he plans to take him to America, as his son will inherit his business. While visiting Manta, Mansumi informs him about Midori's investigation into Yoh's background much to the shock of his son before he slaps him. Mansumi scolds his son about Yoh being a bad influence before being informed by Midori that he has a meeting in Moscow. He soon leaves the room but not before telling Manta to not see Yoh again and that he also finished the paperwork for Manta to go to America where he would study at an American University.

Shaman Fights Second Round
Eventually, Mansumi brought a large fleet of ships to the Shaman Fight's isolated island location where he is seen silently sitting on his ship chair before being giving orders. After Hao's followers were killed off, Midori then contacts Mansumi to tell him that they were all annihilated and the Shaman Fight will end soon, while Mansumi thinks to himself that the Great Spirit is close.

Invading the Plants
Midori later gives Mansumi information on the continent of Mū, saying it is a "world class discovery". However, Mansumi informs him that they did not come here to make a discovery or seek the legend but to seek the wisdom of the Great Spirit. In addition, he also says that he already arranged necessary preparations to retaliate Hao's attack and hired Hans Reiheit and Amano Teruko to be his personal guards. Manta eventually finds out that Midori has been contacting his father about the Shaman Fights and of the Great Spirit. In addition, Anna destroys Manta's phone, revealing that Mansumi ordered Midori to put a bug on it to spy and using Manta to gather information to track down the shamans.

The next day, Mansumi and his sheep fleet prepare to attack the island, eventually Hao single-handedly destroys nearly all the ships except the one Mansumi is on board. Commander Sato questions Mansumi on who Hao is to which Mansumi responds that he can read minds and that he should not lost his cool just until Hao shows up finding Mansumi.

Following his defeat, Mansumi is captured and held hostage by Anna, who agrees to let him talk to Manta in private. Hao also revealed that he spared Mansumi due to a moment of weakness, as he realized he was facing people who are parents as Usui Lycan was also captured and made into a hostage.

Anime/Manga Difference
Mansumi does not appear in the 2001 anime series.