Sigma, also referred to as Commander Sigma or The Commander, is the main antagonist of the Mega Man X series.Created by Dr. Cain, Sigma was considered the finest of the Reploids and was the first leader of the Maverick Hunters; peace-keeping Reploids who defend humans against their renegade counterparts. Although he was once honorable, Sigma unexpectedly goes Maverick in the beginning of Mega Man X and rebels against humankind. He defects to the Mavericks and assumes the role of their leader. Under Sigma&#039;s command, the Mavericks grow into a legion dedicated to the extermination of the human race. 

The year is 21XX. Reploids are commonplace now, after Dr. Cain rediscovered Dr. Light's old lab and based several designs off of Dr.Light's original, called "Megaman X." X, meanwhile, has joined the Maverick Hunters, and works with unit leader Zero under the command of General Sigma. It is their job to terminate rogue reploids, those who have become violent.
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(Source: Anime News Network)

Mugihito is a Japanese actor, voice actor and narrator from Musashino, Tokyo. Mugihito was formerly credited under his birth name and also Mugihito Amachi (天地麦人).

Mega Man X video game in manga form. Repliroids, developed to protect humans, have begun to attack humanity as being superior to it. However, the developer of the Repliroids has anticipated the worst and left the Repliroid who is constantly evolving to protect humanity, Rockman, as a last trump card.

Robots Mega Man X (Rockman X) and Zero battle against an evil robot named Sigma.

Bundled alongside, the 10 pages oneshot features Iwamoto Yoshihiro's take on the original Megaman X5 ending, using the version of the characters first featured in his adapations of Megaman X1 trough X4.