User blog comment:B214/General Discussion/@comment-24098614-20180331210136

I see that Issei has a long way to learn because if Mirana in Volume 23 can cause him to be distracted because of Breasts it will hurt him in the long run as a master.

He has to learn to ignore Breasts as a diversion because his opponents know of his tendencies to lechery, and will use this to their advantage because if Issei was fighting Sona he would lose against her knowing how tactical and smart she is.