25-35 Years (excact age unknown)
Yamaki runs hypnos, a secret program there to protect the population from hostile digimon. Yamaki takes this very seriously and will do anything to stop the advances of the digimon.
Very strong willed and determined to do what it takes to achieve his goals. If it means hurting some people along the way, fine. Will even go against his superiors without thinking twice. Though he hates all digimon at first he has a change of heart after he sees that the Tamers really are the only people who can stop the devas and their sovereign.
Though Yamaki seems to be an emotionless machine but behaves the way he does out of his concern for others, which he occasionally does show.