Who is the boy in the coffin in the last episode (of the Gemini of the Meteor)? Who is the boy in the coffin that wakes up in the last episode of the second season, Gemini of the Meteor? What significance does he play? Why does he look like Yin?
If it's sticking vaguely close to the manga it's Kagutsuchi (the being unknown) who is created when Izanami (Yin) and Izanagi (Hei or Shion) bond as predicted in the Mikata Documents.


  Izanagi gazes upon the false sea bottom, waiting for Izanami. Izanami
  will cross the sea bottom and eventually the two will meet. When they
  do, heaven and earth will split in two, and there the Gate of Hell
  will open. From the Gate will come forth one, a being unknown. And
  strife will continue for eternity.