Hi there. It's me (yet again).
OK, most fans think Number Six=Aogami Pierce (would explain why Aogami is the only recurring classmate of Touma that isn't involved in the Magic versus Science confrontation (not even Daihasei Festival), just as Number Six is yet to be shown). But, have you ever considered that a Kihara might be #6? Railgun shows that just about any Kihara can be an Esper, yet still be a psychopath and consider Espers 'lab animals'.
Also Amata, Gensei's son and You-Know-Who's teacher, supposedly has a son involved in the Dark Side of Academy City (by Kihara standards it seems that Amata was a very good father). What about him? It doesn't seem impossible that he works independently or in an organization that is so deep that only Aiwass,Aleister and Heaven Canceller (as well as Gensei) would have any idea about what does he exactly do.
Don't get me wrong, but isn't it awfully suspicious that Pierce's name isn't revealed yet?! Could that be him? Or is it that #6 is a foreigner? Perhaps his power is too of a Gemstone like Gunha, but a bit easier to understand?! Not even Motoharu doesn't seem to know everything about everyone in Academy City (and he is a double-double(+ another 'double' for each time he was caught (double)spying)agent.
So, to wrap this up, what the you think? Insane, sheer speculation, farfetched or actually might be on to something?