Is Yatogami Kuro a strain?

I doubt that Kuro is a strain. From what I´ve read and heard, those powers are his for having been a member of the colorless clan. Apparently, the powers of that clan vary depending on the current king and the person itself.

Also, I think they don´t lose their powers when they lose their king. I´m just guessing this but rather than losing their powers completely when losing their king, I think they just lose most of their powers. Like, they still have those powers but they´re a lot weaker than they originally were.
At least that´s how I explain that Yata and Izumo could still use their powers in the movie even before Anna actually awakened as a king.
Additionally, them not completely losing their powers would also explain why Yukari has two auras (though I can´t remember having seen him using his colorless aura) even though there is no colorless king.