Overview
The classic Mega Man series consists of ten main titles including the original game, as well as all Game Boy and PC titles featuring the original design of Mega Man. The classic series is considered to be the origin of the story, with Mega Man being the first installment, and continuing with ten direct sequels. Chronologically after Mega Man 8 comes Mega Man & Bass, followed by Mega Man 9 and Mega Man 10.
Although the classic series has yet to reach an ending, the storyline shifts to the Mega Man X series, followed by Mega Man Zero, Mega Man ZX and Mega Man Legends. Although it is confirmed that the Legends series takes place sometime in the distant future after the ZX series, there is an uncertain amount of time as to when it actually takes place. All series follow one continuous timeline except for Mega Man Battle Network and Mega Man Star Force which exist in an alternate universe (one in which network-technology flourished instead of robotics technology), with Star Force occurring two centuries after the Battle Network series.
The official source book Rockman Perfect Memories outlines the Classic, X, and Legends series and makes mention of the Battle Network and Zero series (which were fairly new at the time of the book's publication). While the ZX and Star Force series were not yet conceived when the source book was published, Capcom is explicit within the games themselves regarding their placement in the timeline(s).
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