Board Thread:General Discussion/@comment-1875854-20150221232630/@comment-1875854-20150223204805

Well, based on this http://naruto.wikia.com/wiki/Nature_Transformation#Yin_and_Yang

Spiritual Energy comes from the mind.

Physical, from the body.

Yin Release, is still chakra. Just it has more spiritual energy than physical. Yang Release is vice versa.