User blog comment:Jopjopjop/Volume 18 Spoilers/@comment-74.110.108.150-20140910120029/@comment-24502975-20140910141328

Azazel points out in this volume, before he finds out Irina was his first kiss, that Ise has become less perverted.

That, and it's already stated he gained his perversion from the old man with the picture show.