User blog comment:B214/Light Novel Volume 16 spoilers/@comment-9339850-20131031065534/@comment-1392308-20131103034121

@B124:

That's true, big sister types is one of his fetishes. lol, I guess that's why Xenovia specifically picked out this particular Eroge this time.

Rias' has enough actions, lol, she gets to sleep in his bed every night, same with Asia. Though I do wish the dates mentioned at the end of Volume 12 were shown. Hopefully a special series of side stories will cover them.