High School DXD, Vol. 11 (Light Novel) (novel)

The time has finally come. All of Issei's effort punching gods and heroes has paid off. He's been recommended for a promotion to a middle-class demon! Unfortunately, he has to take a test to seal the deal, and it bangs right up against his midterms! Now the poor pervert is studying twice as hard.

As if that wasn't trouble enough, Ophis, the Infinite Dragon and leader of the Khaos Brigade, shows up on Issei's doorstep asking to stay with him for a few days! It doesn't seem like the trouble will be letting up soon. Hopefully, Issei can make it out in one piece...