User blog comment:B214/Light Novel Volume 16 spoilers/@comment-1392308-20131019074749/@comment-1392308-20131019075454

Ah thanks.

Perhaps he'll tackle that hurdle next volume and attempt to learn some magic. That may be why it focuses on Rossweisse.

Lets see, this would be a good opportunity for that reincarnated devil in the top 10 of the rating games to appear. He could advise Issei on how to become stronger without using a Sacred Gear (considering he doesn't have one which may or may not be true).