Board Thread:Naruto Discussions/@comment-26993711-20160319001508/@comment-26636534-20160319095628

Why couldn't Obito use Kamui? He has been able to suck in an explosion with Kamui, so it's quite logical that he simply used Kamui to suck in Amaterasu. The other option would simply be to detach his burning zetsu arm and replace it with a new one.