Hitomi

improve their physical strength, regeneration, etc. Over the generations the nanobots degraded and these days don't provide much of an improvement over normal humn characteristics. Due to media indoctrination she wants to become a magical girl, fight evil, yadda yadda. So she grabbed a plastic wand and a ridiculous outfit and sought for evil to fight. One day a voice inside her taught her how to turn that decorative wand into a real weapon (it can transform into an extending chain of blades that slices everything in its way to ribbons, used like a chainsaw) and how to use real magic. Turns out Hitomi is actually a goddess (though she isn't through ascension yet and can't use godly powers. That has to wait until she's 18). Maybe a nearly immortal being is a bit overkill for fighting evil but that never stopped Superman, either.
Hitomi comes from an "alternate dimension" (best way to describe it in few words) that appears to be Earth 200 years into the future. Where she comes from all humans are infused with nanobots to