Asakura Hao is the main antagonist in Shaman King. He was born Asaha Douji in Japan during the Heian era. During his third life he becomes the twin brother of his descendant Asakura Yoh. His name translates to Leaf King. He is the most powerful shaman in the entirety of the series. His childhood is told in the manga side story Mappa Douji.
During his first life, Asakura Hao was constantly surrounded by the horrors of war and thus saw the world as a grim and dark place, until he met the small demon Ohachiyo, who taught him all the positive aspects of life. However, after an accident involving Hao's first Over Soul, Ohachiyo became a permanent part of Hao and cursed him with the very dangerous ability of Reishi. As he grew into an adult Hao became a relatively peaceful man who sought to help the people around him, and thanks to him the Asakura Family prospered. It was because of this gentle and kind nature that he took in the cat Matamune, who wound up becoming what he considered his "only friend."
However, his Reishi abilities became too strong and eventually went beyond his control. The negative emotions and thoughts of others were constantly overwhelming him and, since he was unable to turn his Reishi off, the deluge of negativity eventually created a demon inside his own heart. The internal confusion and disorder that was also created eventually led to his desire of creating a Shaman only Kingdom on earth and drove him to become the Shaman King in order to reach this goal.
In his third and most current incarnation, Hao is usually calm, cruel, and all smiles. The occasions when he is really angry are very rare and when he is angry with someone, that person is usually killed and burned to their soul by The Spirit Of Fire. He also likes to watch Shaman Fights, particularly those that involve strong Shaman, and Asakura Yoh. He is not only interested in that, but also claims that when Yoh reached his limit, he will eat him to become the strongest Shaman.
He has shown some dislike of being given family titles, as he glared at Yoh in the last chapter when the latter called him "Nii-chan," and his face darkened when his nephew, Asakura Hana, called him Uncle Hao. Both times he told the person not to call him that.