In the show, hints are dropped that Haruko is on Earth on the pretext of fighting Medical Mechanica (more apparent in the manga). Her conflict with the mysterious organization overlaps perfectly onto Naota's own adolescent experience-- Haruko represents the spirit of freedom(it's no coincidence that she carries a guitar-- connotating a link between her and Rock and Roll, which has always had a rebellious streak to it): she lives without being really tied down to anyone or anything. Her pursuit of Atomsk would imply otherwise, but that, too, is part of the psychology of the wanderer: travelling around, searching for something that the searcher knows can never be really obtained--it's the journey that counts. Medical Mechanica, however, stands for conformity (obviously). When Naota gets absorbed by the Terminal Core in episode 6, we're shown a planet with many MM facilities 'flattening' it's surface. Amaro also says that "They're flattening out the wrinkles so you can't think." In the manga Haruko states that "brainwashed slaves can do nothing but enjoy their slavery." It doesn't hurt that all the MM buildings look like clothes irons. They're also keeping Atomsk (the Pirate King, thus the ultimate rebel) imprisoned and powerless there, which implies that their power is nothing to be trifled with. Ultimately, the struggle between Haruko and MM is a metaphor for conflict between the forces of individuality and conformity within all of us that must be faced as we become adults: it's the decision we must make between a blanket of comforting mob mentality and truly becoming individuals.
(Damn, I'm pretty freakin' long winded.)


