User blog comment:B214/Question and Answers 2/@comment-75.107.224.61-20140524000659/@comment-24098614-20140524021431

The ability of "Dragonification" doesn't suprise me at all because the body of Issei comes from Great Red so I assumed that he could do this at some point in the story because he is no longer restricted to the frail Human body that he had before in the beginning of the series.

The best thing that happened to Issei was his death of sorts because he managed to get rid of his old body but also get a boost to his lifeforce because I am still curious how much lifeforce he has right now.