In the coldest dead zone of the universe, where there is no matter and no life, there is only the limit of the universe. Out there, dark energy accelerates and expands space and time, stretching the universe further into infinity. Shadow-san did not exist at the time when the call of the Observers spread through the multiverse. But in response to the Observers, the edge of the universe issued forth a wave of energy and consciousness.

At first, Shadow-san was just a mass of energy with no defined shape. Later, the entity decided the image of a ninja was cool, so it decided to manifest in that form. And that is how Shadow-san's current appearance came to be.