Board Thread:Fourth Databook/@comment-4366149-20141122004623/@comment-25626003-20141203174206

His left eye shapes the flames, the right eye casts them. The manga doesn't depict it clearly in that chapter but I know in the anime I saw him use his left to shape the black flames. You have to remember that Kagutsuchi and Amaterasu are two different techs, but utilize the same flames. Kagutsuchi is controled flames out of his left eye, while Amaterasu is wildfire that spreads uncontrollably.