Mitsuo Yamaki

Mitsuo Yamaki is the mysterious leader of the Hypnos Organization, a major antagonist (later ally) in Digimon Tamers, and one of the few human antagonists in the Digimon series. He was voiced by Susumo Chiba in the Japanese version, and Steven Jay Blum in the English version.

Digimon feud and Forgiveness
Yamaki is the leader of Hypnos, a governmental organization in charge of watching the Digital World and prevent the entrance of Digimon in the Real World. In his vision, every Digimon is considered a threat and must be immediately deleted. When he finally realizes that not all Digimon are evil, he allies with the Tamers to defeat the Digimon Devas, paying for his past deeds. However, the Devas were just the beggining...

Trivia

 * Whenever he's nervous, Yamaki starts to flicker a small lighter, indicating he possibly smoked in the past.
 * There are a few, rare times when he shows any emotion or even removes his sunglasses.