And now, to make sure Misaka doesn't go and blow up half the plot on her own/before other people can get involved...

[list][*][b]Name:[/b] Shirai Kuroko
[*][b]Age:[/b] 13
[*][b]Appearance:[/b] [url=http://4.bp.blogspot.com/_UXIrLQi4S7Q/TG3e1XtLRDI/AAAAAAAAA2o/Tkk6GO09iaI/s1600/21kuroko1ep1.png]"Judgement desu no!"[/url]
[*][b]Personality:[/b] There is one thing that anyone who meets Kuroko knows about her attitude, it's that she is ridiculously, and somewhat worryingly, into Mikoto. It's not just lust, and she's quite capable of being a good friend and highly reliable when her self-control hasn't slipped, but... well, propriety seems to go right out the window when Mikoto's involved.
She's also, despite using overly refined speech for casual conversation, rather blunt with her opinions and suspicions, which means that her tendency to dismiss things such as urban legends and rumours is also quite hard to miss. She's not entirely bad, though, as she's usually quite laid back and has a strong sense of justice. Predictably, this means not backing down when in a losing battle.
[*][b]Level:[/b] 4
[*][b]Power:[/b] Teleport. It is, as the name suggests, the ability to teleport objects and people--including Kuroko herself, with her level. Teleported objects have the power to displace whatever's in their destination, which is understandably quite dangerous. It's not an ability without its drawbacks, however: since it relies on eleven dimensional mathematics, it's not exactly a reflexive ability and it isn't possible to pull it off whilst severely distracted. It's also got a weight and distance limit, as well as a delay between consecutive uses. In order to actually have ammunition, Kuroko has metal darts strapped to her thighs.
Making up (somewhat, she seems to always get hit anyway) for her power not being something that you can constantly use is a level of martial arts skill that nonetheless faces a quite unfortunate problem: she's still less than five feet tall.
[*][b]History:[/b] Kuroko joined Judgement the year before joining Tokiwadai, and after joining said school became rather enamoured of Tokiwadai's Ace. This lead to finding a way to become Misaka's roommate... and subsequently she's ended up as said Railgun's best friend, despite her actions.[/list]