Mega Man Maverick Hunter X: The Day of Σ

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 "Mega Man X". X, meanwhile, has joined the Maverick Hunters, and works with unit leader Zero under the command of Commander Sigma. It is their job to terminate reploids who have become violent.

Mega Man X: The Day of Sigma

In a prequel to Mega Man Maverick Hunter X, the Maverick Hunters led by X and Zero, under the command of Sigma, face reploids who have become violent.