You can't, without the "main heroine" armor you're just a stage 4 boss.
Also, if you came from the future shouldn't you know exactly what your past self would do and avoid it for certain victory? Or did you lose willingly by accepting destiny can't be changed? Or perhaps, you did change your path, but then again destiny changed too and allow your past self to defeat you? However, shouldn't that be incorrect in the matter of space and time, since by getting defeated and changing history, your past self does something you didn't do in that exact space-time? Then your memory can't access that which she has in this very moment, thus causes a massive breakdown from within, isn't that right?

In the end, no one can defeat Reimu

...Not even Reimu

touhoufannumbah249 said:
In the end, no one can defeat Reimu

...Not even Reimu

It is like Dividing by Zero. Only the end of the galaxy will happen.

I woulnt mind something like this being the end of Zun's touhou games (yeah, for more I love him and his work, he wont be around forever, and since he works solo, it might be over for official games when he wants to) Reimu for final boss!