User blog comment:Jopjopjop/Volume 18 Spoilers/@comment-24866657-20140619135909

It could be Vali penetrated Rizevim though, as much as I like to see Issei's new powerup, it's enough for him now, and Ishibumi is going to team battle, from vol 14 onward Issei usually fought together with his team, it's no longer one-man-army and the shining protagonist, I like that style.