Per wiki policy, Spoilers Off applies here and all spoilers are unmarked. You Have Been Warned.
Yaha-kui is The Last of His Kind
And has absolutely no company, except perhaps the KADO itself.- Jossed. There are many others.
Yaha-kui zuShunina's ultimate plan is to turn all humans into the same species, or at least uplifted to the same level, as himself
The conversations between Shindou and his mother was blatant foreshadowing.- Confirmed.
- Maybe when the latter decides to bring him back. Tweaked and improved.
- Jossed.
Yaha-kui and other anisotropic beings are Boltzmann Brains
These hypothetical, self-aware entities are supposed to manifest spontaneously in environments of sufficient informational complexity. They never appear in our universe because the anisotropic world is more fertile ground for such development. In the end, Shindou will go with zaShunina in order to preserve the rest of the humans
zaShunina is a bit obsessed with Shindou, and really wants to take at least one human into the anisotropic, so Shindou, being a master negotiator, will exchange himself for the promise of no more anisotropic interference into humanity's universe... And it will work!Shindou will ascend into the anisotropic for our sins (of making sexy information that brings all the anisotropic beings to the yard)