Board Thread:Theories and Speculation/@comment-36512555-20200101053037/@comment-34656247-20200224174420

There is no absurdity present in the contents of the genjutsu used, hence Itachi is portraying in genjutsu, what he's capable of/and can do, the same for Sasuke. Indeed it's happening in the mental realm, but they're still mimicking reality. He not only displayed combat speed feat, but also travel, such as when he got up from the chair and appeared next to Sasuke, if such speed was absurd then using it would be pointless, because it'd just be telling Sasuke that he's under genjutsu. Then he went on to blitz Sasuke in tsukuyomi.. Chapter 636 is also similar.