User blog comment:B214/Volume 21 info & spoilers/@comment-95.90.227.221-20160416005245/@comment-202.62.17.207-20160416145941

To the wikia contributor above me, try to read the spoiler of High School DXD EX, it is a series of sidestories that can only be found in the Blue-ray Discs and it is about Issei's kids 30 years from the future going back in time to the present and meet azzazel for a certain mission.

From the stories there can be some hints on whats going to hapen 30 years in the future and i can assure you it is epic!!! The spoilers of the High School DXD EX can be found on animesuki website