Iji is very sad.
Not only are you responsible for the destruction of a whole race (they had it comming, sure, but it's sad nonetheless) but humans are more or less extinct now too (science tells us you need at least 50 individuals for a human settlement to survive).
and what was that whole story with the purple bows (or whatever they were, I don't remember) it just seems to give you sad memories, and no sister to be found (or did I somehow miss one...?)
Each of those ribbons is a figment of Iji's imagination(Stated by the maker himself and I think a logbook in game mentions it if you've been collecting them well enough). And no, you can't find Mia, she's dead.
There are people that survived the alpha strike that weren't at the base. It wasn't a full power strike(The Komato one would've killed everything though). I think Dan and several other sources mention that it's likely not all humans have died yet, Iji even mentions this during the last dialogue with Tor.
The null driver is a fun crazy weapon. But personally I think the scrambler is one of the best items in the game. All of Asha's dialogue while scrambled is
Asha: PEW PEW PEW
Asha: HONK
Asha: TOOT TOOT
Asha: (Heart symbol)
Iji: dot dot dot
Iji: Look, I'm a cyborg. You don't want to mess with that.
Dan: Missile ponies aren't everything in life, you know. But I have three, so I still win.
(Next level)
Iji: You... y-you promised me a pony... with missiles...
(End of next level)
Dan: No missile ponies for you.
Dan: Oh yeah? Well I got the funniest Scrambler quotes. I win.