Bass was born of the remnants of PharaohMan's data, which were extracted from the Navi by Wily, who wanted his Ultimate Program. Bass had no memories of his previous life as PharaohMan until he abducted MegaMan and read his memories, learning his origins and awakening his "true self".

In the manga, Bass made his first appearance in Volume 3, when MegaMan and Protoman were investigating the UnderNet. Similar to his game counterpart, he faced Serenade in the past, and was determined to wield the same power one day. Constantly coming into conflict with MegaMan, ProtoMan and their operators, Bass would eventually be taken away by Dark MegaMan (Dark Rockman) and LaserMan, who had intentions to change the world into the Dark Kingdom. Dark MegaMan subsequently tried to absorb all of Bass' power to become the ultimate being, but, failing to consume his entire consciousness, was disconnected from the Navi's soul. Bass was then fighting Nebula Grey, having drawn by Nebula Grey's dark power. Bass proceeded to attack Nebula Grey, but to no avail, leading him to fuse with MegaMan to create BassCross MegaMan. After Nebula Grey's defeat at MegaMan's hand who used Beast Out, he destroy Dr. Regal's submarine. He reappeared in the underground during the fight to see who could obtain the legendary program to defeat Gregar. He once again saved MegaMan, this time from Cyberbeast Falzar and then absorbed Falzar to once again be MegaMan's equal in terms of power. After the Cyberbeast merged and slowly deleting the real world, Bass eventually assisted MegaMan and gave him all of his power to defeat the Ceyberbeast after encouragement from Serenade. Compared to the anime and the game, Bass is portrayed having deeper rivalry and friendship with MegaMan.

(Source: Wikipedia)