I don't know how good this is... BUT I TRIED!!!
Any way the explanation...
Key was born with the ability to go anywhere with a key if she thinks about it enough and really feels for it.... unfortunately she is unable to use her power when stressed. Hence why she was unable to teleport back home when she was little.
Her parents were so stressed out that they would lose her that she was put under surveillance at a young age so that they would never lose her... as such she has become starved for adventure and gets to the point were she accidentally teleports into a busy street. She is rather startled since it's been so long... She has tried to to this before but at all those points she was trying to hard and as a result it didn't work. but in this case she wasn't even trying so it actually happened.
it's not shown in this part but as soon as she arrives in the city she gets noticed by Regis.... TO BE CONTINUED O.o
Key is 10
her specialty is locks, puzzles, and sneaking past security.
As she gets more keys shes going to put them in her hair.
shes a very understanding and accepting and tends to become attached to people very quickly.