I realised this only when I was watching the final episode, but Izanami is the combination known as Yin and Yang. That's when I felt that everything clicked, and I felt like I have solved the mystery of the show.
Wikipedia definition of yin and yang:
In Ancient Chinese philosophy, yin and yang (/jɪn/ and /jɑːŋ, jæŋ/; Chinese: 陰陽 yīnyáng pronounced [ín jǎŋ], lit. "dark-light", "negative-positive") is a Chinese philosophical concept that describes how obviously opposite or contrary forces may actually be complementary, interconnected, and interdependent in the natural world, and how they may give rise to each other as they interrelate to one another.[1] In Chinese cosmology, the universe creates itself out of a primary chaos of material energy, organized into the cycles of Yin and Yang and formed into objects and lives. Yin is the receptive and Yang the active principle, seen in all forms of change and difference such as the annual cycle (winter and summer), the landscape (north-facing shade and south-facing brightness), sexual coupling (female and male), the formation of both men and women as characters and sociopolitical history (disorder and order).[2]
The very reason that the anime plot itself seems so mysterious is because this whole anime is an embodiment of the meaning of yin and yang. It's the author's attempt at creating a story revolved around the philosophy of yin and yang.
~~~~~~~~~~~***Spoilers ahead***~~~~~~~~~~~
My views about the plot of this show:
The very essence of this show is the author's view of life from a traditional Chinese point of view, i.e., the principle of yin and yang, as mentioned before. The idea of yin and yang is not a simple one to comprehend, but once you know that the show revolves around that idea, things suddenly start making a lot more sense.
What relation does the Astronomy Department have with contractors' superpowers, much less what's going on with the Gate? Once you know that traditional Chinese beliefs regarding cosmology are intertwined with the philosophical concepts of yin and yang, you begin to see why the author chose to do things the way he did.
The same logic applies everywhere else:
Contractors and normal people. One apparently does not feel emotions and the other does. One has no dreams and the other has. Opposite in many ways.
The past and the future. Both are themes that were constantly brought up in the show. One is changeable and the other is not. Stars of the past and stars of the future. Opposite in many ways.
The old Earth and the copy Shion created. The filthy world we live in and the dark truth of it all, versus the ideal world Shion envisioned for those he loved and cared about. Opposite in many ways.
Shion is the only one who figured out how to make sure that all those who have lost something due to the inevitable prophecy have a way of finding the things they have lost. Contractors have lost their humanity not because they gained new powers or lost their emotions, but because the rest of humanity has rejected them.
For that reason, Shion sacrificed himself to create a copy of Earth where all the contractors will finally be able to live a normal life as humans rather than the killing machines that their governments and secret organisations forced them to be.
Some final thoughts on this show:
This may be a bit of a stretch, but I think that the very idea of clarity versus mystery is one of the main topics tackled by the author in his attempt to give a shape to the philosophy of yin and yang. I always wondered why the show had a mystery genre tag even though the show is not your everyday detective show where someone solves seemingly impossible cases, albeit the show actually having a detective who did barely anything for a few episodes.
The mystery of what is behind everything that happens in this show is the author's attempt at creating a setting where yin and yang have free reign. At least that's the way I see it. In my opinion, the ultimate embodiment of yin and yang in this show is not something tangible that you can explain to someone in a matter of minutes and have them say "ah now I see the point"; they would have to watch the entire show and think for themselves and reach a conclusion of their own.
This is what I think the author was trying to ultimately achieve when making this story. The lack of proper explanation for everything was done not to confuse the viewers, but rather to convey to them the basic idea of yin and yang and have them reach their personal conclusion. After all, isn't that what philosophy is about?
