User blog comment:Cookievalenzuela666/harem predictions......./@comment-79.45.189.189-20140329020354/@comment-1359322-20140329065049

If undergoing that ceremony means they become engaged then Rias and Riser would have undergone that otherwise they wouldn't have become engaged, Rias and Riser were definitely engaged until Volume 2. That's why i said that ceremony was to test their feelings and maybe Issei's suitability to become the Clan Head alongside Rias. I guess this ceremony is because of the circumstances type of thing. Sirzechs and Grayfia were enemy at one point, that may be why they need to undergo the Ceremony. As for Issei, Issei is a Reincarnated Devil from a normal human without talent or skills and a Low-class Devil to boost, he might not be viewed as the most suitable husband for Rias as many will view. Since the Gremories are known to have deep affections, maybe they want to test to see if their chosen couple are suitable with them.