User blog comment:IamJakuhoRaikoben/Chapter 388: Erza vs. Minerva, Review./@comment-24053170-20140614051148/@comment-24053170-20140614055440

Zeref himself said that End has never met him. when he stopped time and appeared to natsu inside cube. Zeref said, that either Natsu or End will meet him, but not both.