Bubbleman is a Dark Lord navi, and under the command of Shademan. More often than not, Bubbleman poses as comic relief rather than a real threat, as he continually fails in his missions, usually rather embarrassingly.
Like many of the other Dark Lords, Bubbleman has no operator. However, he does have a rather odd relationship with Shademan, in what we can only describe as a very loyal "friendship" of sorts. Bubbleman tends to add the word "puku!" to the end of every single sentence he says, much like Higure always adds "demasu".
Even after Axess concludes, Bubbleman remains an important character all the to the very end of the EXE genre. Even when he finally befriends Rockman, he still proclaims himself a Dark Lord.