User blog comment:B214/Volume 23 discussion blog/@comment-77.188.220.109-20170502211011/@comment-82.58.59.197-20170502212913

AxA and ExE should be the names of the next form of Issei's power.

AxA should be the power of Issei + the power of the Great Read that he possess because of his body.

ExE should be the comination of Issei's power (including his Sacred Gear) + Ophis' power + Great Red's power, his ultimate form.

It could be also in the opposite, so ExE being the Great Red power and AxA the combination of all of them, but in any case the outcome is that.