User blog comment:Jopjopjop/Volume 19 Spoilers/@comment-104.7.80.176-20150603035954/@comment-98.227.238.52-20150603074338

Whoa, there take it easy I think what they mean is that Rias had already sensed something was inside Issei before that happened. When she and Akeno were talking about him she said that he interested her. She had the chance to speak to him then, but instead she just gave him a leaflet and watched and waited. I mean why take the chance that he would make a wish. What if he didn't. And given that this is Issei we're talking about I highly doubt he would have said no anyway. Though, she would have had to show him some proof that she and her servants were really what they said they were.

And according to Azazel they were keeping him under surveillance to make sure that his sacred gear didn't go berserk. Raynare was only suppose to observe him not approach. Which is something that they normally wouldn't do. And Rias knew she was a fallen angel. Shouldn't that have given told her something was up.