Board Thread:Naruto Discussions/@comment-24847491-20140920090914/@comment-1512913-20140924101533

No, it never was, people just wrongly assumed so and played dumb since. Blaze Release is an advanced chakra nature. As stated by C, all Sasuke does with his right eye (Kagatsuchi) is apply shape transformation to the black flames. Shape transformation doesn't alter a nature, shaped wind is still wind etc. therefore the nature doesn't come from Kagatsuchi, meaning Amaterasu itself has to be Blaze Release.