Well i choose Kill because... it's Killy...

but... here my thought's on all of "Blame!" World. (some of them came to me after reading this topic)

Question's and answers
(correct me if i am wrong in any of them)
Killy's mission
q: What is Killy mission ?
a: Killy must find clean (without any mutation or virus (mb n5s virus ??) Human-net-gene-carrier.
q: what is "Human-net-gene-carrier"?
a: it is human that can access net-sphere from outer world.
q: What is net-sphere
a: It's some sort of virtual reality where human Consciousness can live by itself (something like Matrix)
q: Why must Killy find such being?
a: it's mission given him from GA (Goverment Agency)
q: GA ?
a: Goverment agency - the Goverment of the Net-sphere
q: Why do they want such being ?
a: well, Society of Net-sphere was hit by some sort of Disease/Virus/mutation process that prevent any of net-sphere dwellers to control any of net-sphere activity

Who is Killy ?
q: Who is Killy?
a: Like hell i know... ^__^ (jk) Killy is One (and maybe only) agent of Presafeguard system.
q: presafguard system?
a: Sort of agency that was BEFORE creation of Safeguard.
q: Safeguard (sg) ???
a: Safeguard is an аrtificial life, created, on request of GA, to clean off humanity from people that do not possess net-sphere-gene
q: Why Killy fighting with them ??
a: *sigh* Well it's true that GA, in begining, controled SG, but since Disease/Virus/mutation hited all dwellers of Net-sphere, they lost control over SG and they (sg) became independent. But main objective for SG was same as before - cleaning humanity. And Killy is trying to find clean human, so they sometimes confront each other. and on a side note. Do not confuse SG with SG Agent (like Sanakan and Domo with Iko)

q: so... the story so far ???
a: ok. that's my IMHO and nothing more, but you asked for that....

If we would read through all of Blame! Related stories (it's Blame itself. of course NoisE, Blame!NSE, and apparently Biomega) we could see this.

if we assume that Bimega is pre-prequel to Blame! - Apparently Net-Sphere project began as measure to Protect from N5S virus (since it's only hit the body, and only after that consciousness). but something go wrong and net-spher and megastructure began to expand without controlling. it's a mystery why it took 'bout 9000 years to dispatch agent to such mission as was given to Killy (methinks that he wasn't One and Only GA agent, it's just he is one who succeded), but here we are. Killy is looking for human with clean-net-sphere genes.

As for Zouich and Susono - Zouichi is looking for surivors and those who adapted to n5s, Musumi going wild as newest version of SG agent, who lost control, and main char of NSE (which i bielive is boy which Killy saved in begginig of Blame!) is cleaning world from last of Silicons and SG.

oh. and if Biomega IS pre-prequel - that means that Zouich might be Killy.
well Look at it.
Zouichi is synthetic human, so is Killy
The SG and net-sphere project dosen't began, and Zouich is Agent of THI (which we can consider as Pre-guard system)
well in vol2ch11 Zouich is look more like Killy (yeah. yeah. i know. Nihei not good in drawing diffirent faces )

on more thought on Biomega.
In Omanga scanlation there is page in the end of vol 1. on that page long-haired man/woman in same uniform as Zouichi holding a gun. and in left-low corner there is Figure "2". i was thinking, what's that mean. than i came across raw of pre-chap to biomega vol 2. where Some man/woman in same uniform as Zouich is brutally killed. and in the end of vol2chap11 there is some char-table. and it say's that person, who brutally killed is He (E-G scanlation) and he is also agent of THI. Ok. That make sense... but what dosen't make sense is that in the very same table it say's that it's MAIN char (means Zouichi) who forcibly made to escape Hinoto, in rocket.
so is it Typo or i just don't get it ??

p.s. Sorry for my bad English.

Well, It's pretty certain that Killy is either a Safeguard that's been reprogrammed or a cyborg sent by the Control Authority. Also, his GBE doesn't work in Toha, so while it isn't explicitely stated, I think it's almost a definate that he isn't from Toha.

If i remember correctly "Killy" is agent of "Pre-guard" system. So he couldn't be Reprogrammed "Safeguard". And "Killy" isn't look like cyborg, he is more like Synthetic human. (like "Zouichi")

as for GBE, we do not know where Killy have gained GBE.
and of course if "T.H.I" was the one who developed such weapon, it would be wise of them to defend them-self from such destructive force.
It seems strange that first class weapon doesn't work only in "T.H.E"

When Nihei will decide to create a story about the past of Killy he will say it very clearly...