User blog comment:B214/Volume 22 spoilers/@comment-95.90.227.243-20160720180259/@comment-95.90.227.243-20160720184317

yeah you are right, do you think issei has trained in secret before the Cup with some God Class Being like Ophis or Lilith.

I think that Issei if he trains really Hard and focus of his Training than he can became a Dragon God Class being or not ? He could become the Eternal Dragon God :D would be cool, but no one knows exept the Author, it can happen everything is possible if the Author wish it and the Editor :D