User blog comment:Crimson and Darkness/Volume 25 discussion blog/@comment-86.149.138.216-20180306193353

I have to say the more I think about (ExE) the more I think the only reason needs It is because when Vali has seen AxA It force him to find something to counter it so that he will become strong enough the handle the full power of (DxD L)  and then they will face each other with full powered versions of DxD G and DxD L. If this happens Issei will need a power Vali can't divide with DxD L that is what I think ExE is.