Board Thread:Naruto Discussions/@comment-24847491-20140920090914/@comment-1512913-20140920095715

@Itachi, his point is that Amaterasu itself is of Blaze Release nature. All Kagatsuchi does is add shape transformation to Amaterasu. Adding shape transformation to a nature doesn't change its nature, so logically the blaze release part has to come from the original technique.