User blog comment:B214/Light Novel Volume 16 spoilers/@comment-9339850-20131031065534/@comment-1359322-20131103032448

True, Xenovia and Irina hasn't received much spotlight since introduced.

But Xenovia is failing to understand something, it's not that they can't keep up with the "older ones", they were never in the same place as them in the first place, one of Issei's distinguished fetish is with them after all. As for the "younger ones", Issei isn't interested in chibi as he said, so they are still safe to a certain extend. Won't be long though.