Board Thread:Theories and Speculation/@comment-25645405-20150719020101/@comment-3568954-20150730101832

KuroiToketsuHoshi

Wrong. Amaterasu is a rare ability its highly unlikely they both would naturally have it Itachi programmed sasukes eye to respond to seeing Obito and when he does he would use Amaterasu on him. the sharingan can sync to other dojutsu Obito did this to sync with Kaguya's Rinne Sharingan and Sasuke did this to Sync his Rinnegan with Obito's this is all that happened he used his ability to make sure that Sasuke gained Amaterasu when looking at obito

you point out that he used Transcription seal Amaterasu yet don't even read the article on said technique this is what it states "This is a technique that seals the technique Amaterasu within the Sharingan of another person. After being sealed within the person, it is involuntarily activated (indicated by the person's Sharingan taking the form of the sealer's Mangekyō Sharingan) when the eye sees its target, which is predetermined by the user." so you see There is no guarantee that sasuke ever would have awakened it if it wasn't for Itachi when sasuke fist used amaterasu his sharingan took on itachi's Mangakyou sharingan form temporarily this was the activation it would never have activated in sasuke otherwise

the only natural Mangekyou sharingan ability he has is his blaze release