Col. Dan Dastun is one of the main protagonists of the anime series The Big O. He is a Colonel (formerly Major) in the Military Police and Roger Smith's former commander, though Dastun still maintains contact with him due to the latter's job as a Negotiator. He is also one of the few people who knows about Roger's affiliation with the Big O.
He is voiced by Tessho Genda in the Japanese version and Peter Lurie in the English version.
Dan is a tall man in his late forties or early fifties, with a moustache and black sideburns. He is usually seen wearing the Military Police uniform, which consists of a white shirt, brown tie, brown trousers, brown coat, and a military hat he wears on his head.
Roger describes Dastun as a "hard-nosed cop". He is completely devoted to the force, and has more pride in the Military Police than anything else. However, he is also rather hot-headed, and is usually seen frowning. He is rather cynical, having a low opinion of the Paradigm Corporation, and outright states that he doesn't trust Alex Rosewater.
Much like Roger, Dastun is very professional when it comes to his work; he believes that jobs of the MIlitary Police should be left to the Military Police and always expects Roger to remember his position as a Negotiator. When Dorothy becomes the witness of a terrorist bombing, he takes her into custody to learn what she saw, telling Roger that it's a standard procedure, though he does give Roger his word that she won't be harmed. Although the two butt heads from time to time, it is clear that Roger holds Dastun in high regard, believing Dastun's job to be just as important to Paradigm City as his own.
Dastun's pride as a member of the military police puts him somewhat at odds with Roger after he resigns from the force, and he expresses an extreme amount of irritation every time Big O appears. At first this irritation is passed off as disliking the vigilante nature of the Megadeus. However, as the series progresses, he reveals to Roger that his irritation stems from the fact that the Military Police do not have the ability to protect the city adequately due to frequent Megadeus attacks. This requires Big O to step in fairly often to counter these attacks, which Dastun feels robs the Military Police of its purpose.