User blog comment:Mnzombie/Issei's Peerage/@comment-24098614-20140110005926/@comment-16281343-20140110071420

Issei should have been a High-class already if achievements are concerned, the devil society just wants him to take part in the usual process where he needs to be a Mid-class devil first. Sirzechs already said that his promotion to become High-class will come sooner that later.

~Issei isn't that dumb so a little time learning will guarantee him in becoming a High-class Devil.