User blog comment:B214/Season 3 discussion/@comment-178.128.187.173-20150913203258/@comment-26108673-20150930010222

It's almost like Xeroz said up there. He had a problem with advancing relationship with the girls, for example, to take a step forward and get along with girls. To be precise, he had a problem to get along with girls, as Raynare's actions have been bothering him until volume 10, where she didn't want Issei to call her by name, or that every plan he did with her in their date was boring. So, that led Issei to be wondering if it was really okay to call Rias by name, or if the girls were having fun while going out with him. That's it.