High School DxD manga volume 10 features story by Ichiei Ishibumi and art by Hiroji Mishima.

Now that training is done and Rias's peerage is back together again, it's time to party! With just one day before the big game, tensions are running high, and things only get worse when some party crashers arrive! Issei is eager to show off the results of his training, but he still can't activate his Balance Breaker...or can he? Looking at Rias, his eyes drift downward, and he realizes what he must do...Is there room in Minato's harem for one more?