User blog comment:B214/Question and Answers 6/@comment-29362784-20170329203907/@comment-29963364-20170329205110

That's true. The name for the agency that Issei is supposed to lead in the future is called ExE.

But the double-letters represent Issei's power-ups as well.

ExE is supposedly a power-up Issei will get when the "other world" invades.