User blog comment:Jopjopjop/Volume 20 Spoilers/@comment-79.112.26.210-20150805141055/@comment-26285797-20150806192735

@B214 excellent point.

@anon I don't believe Diabolos Dragon mode is a King promotion, but something that goes beyond. Ddraig stated it is a deification, Issei is effectively becoming the Dragon God, so, in a way, he has transcended the King-level.