Board Thread:Theories and Speculation/@comment-6769189-20150307180344/@comment-17623-20150309001328

But Sasuke does have Yin Release. Or can use it. Or something. Yin-Yang is screwy.

Anyway, I share the thought of Blaze Release being the result of Fire Release + Yin Release because apparently Yin Release tends to make crap black, or something as seen when Sasuke got the Yin power from the Sage his Chidori became black. And because Yin Release isn't a "normal" nature transformation, when it is mixed with one that is, the original nature doesn't exactly change but the nature of the element does (Amaterasu being Fire Release despite it not being normal fire).

But that's just my interpretation.