missyrocksurlife
I just finished it myself and I had to go on a google hunt to find answers. Didn't really get much. Sou is either dead and like, in heaven, or somehow they made a totally different universe for her and she's living there with no memories of her old life besides the nagging feeling like she's missing someone. And is Yin alive? And is that thing in the coffin Yin or Izanami or what? I'm not so sure what happened but I feel sad. Probably because it's over XD
Super-necro. My bad.
I just recently finished watching this (yesterday, actually), and had the same questions as quite a few people here. As with others, I found very few answers whilst googling. But I have a few theories of my own, and I quoted this post, because it asks a lot of the questions I feel like may have answers that people just haven't thought about.
Firstly, with Suo and the new world. It is implied by Orielle that the "moon" that appeared is the second Earth, created by Shion. On this Earth, Suo is alive and a human, as is July. Suo is also with her mother and father on this new Earth, with all new memories and interactions. It can be assumed that Hei, Yin, Misaki, and every other character we see in S2 is also on this alternate Earth.
Now. Is Yin dead or alive, and who is the boy that appears at the end of S2? Everyone always pigeon holes Hei's power into "electricity". Hei's ability is molecular manipulation, which he manifests into electricity. "He is capable of special particle luminance, meaning he is able to change molecules similar to how humans are changed into contractors." We see him do this is S1 when he deactivates the Saturn Ring (I believe that's what the cannon is called). So, here is my speculation:
Hei didn't kill Yin. He manipulated the molecules of Izanami and Yin to separate the two, thus returning Yin to Hei (as evidenced by him walking away with Yin in his arms). The boy in the coffin at the end of S2 is Izanami. He resembles Yin because Yin was the host body of Izanami, so he adopts a physical form very similar to that of Yin.
With that in mind, it could be a happy ending for all the HeiXYin fans. I personally think it's fantastic that the two could possibly have been reunited. It could, however, be bittersweet, seeing as Izanami still exists (since Hei didn't kill Yin, and therefore smother out Izanami), and mean that there is a looming demise in the near or distant future. It has been a few years, but I am still holding out for a third season.