Asakura Yohmei is Asakura Yoh's maternal grandfather and he is the current head of the Asakura Family.
Yohmei is an onmyouji who specializes in divination, and fortune telling. His abilities are so skilled that he is employed by numerous important politicians. However, as explained by himself, the future cannot be seen clearly and as such he can only gaze into what might be a possible future.
(Source: Shaman King Wikia)