Board Thread:General Discussion/@comment-6192846-20150613141203/@comment-26871067-20150821233007

I don't feel like the different periods could be the answer here, really. Though the fact that the song seems to skip the Second Period leads credence to it, there's definitely the matter of "other selves", and the fact that it's a mirror being used as a portal seems to hit on a lot of tropes found in parallel world fiction.

Though, with that in mind, the thing with (seemingly) Levia and Behemo is possibly a reference to the muddled relationship of Rin and Len as stated by Crypton, with the ideas of "they're twins" and "they're mirror images" being put forward and then retracted. It resonates a lot with this idea of Levia and Behemo being stated to be twins and then this implication that they're parallel world versions of each other, with the mirror image factor being highlighted there.