User blog comment:SpookyBoogie27/Light Novel Spoilers/@comment-74.110.105.73-20131027183752

This is pure speculation on my part but I think the plot of volume 17 will center on Rossweisse telling everyone in her homeland while she was training during volumes 11 & 12 that she was going out with and engaged to Issei 'cause she was to seem like a big shot to those who teased her about not having a boyfriend, with the goddess Freya coming to kuou academy to announce the wedding, much Rossweisse' dismay, Issei's confusion, and the other girls' jealousy, and you all can probably guess the chaos that will ensue.