User blog comment:DeathGodPrayer/Talk About What You Want!/@comment-82.40.154.8-20140208141219/@comment-24501441-20140208142129

The only connection between Balor and Issei is that Balor swapped their eyes, as shown in Vol 16. I'm pretty sure that Issei's new power up will be something dealing with his white dragons, or learning something new about his sacred gear and abnormal growth.