Aside from fighting game, I never see Reimu fly around without that Yin Yang Balls around her. Did I forget a scene? If not, does that mean she only used it in battle mode, or she can only float with it? (Even though Fantasy Nature is her innate one)
Cus that kinda implied a few thing:
1. That you could still connect PC-98 with Window Reimu, since they're all relied on the Yin Yang Ball as a source of power.
2. If hidden within the balls is the power of the Hakurei God, it's fcking strong itself to be able to FN any opponent (and blow up a planet, counting PC-98), while still in a weakened state. That, once again, put a lot of question into the identity of this god and the Yin Yang Ball itself: What kind of rank do we talking, who made this, and how the Hakurei God came to it current state?