User blog comment:B214/Volume 23 discussion blog/@comment-30924344-20170324232024/@comment-10330822-20170325003251

It maybe a volume for all three. As we saw in this volume, it being "Asia's chapter" didn't prevent Xenovia and Irina from getting in there. However, chances are Kuroka and Koneko will get engaged to Issei after the Rias vs. Vali fight, and Rose will get engaged to Issei either before, during, or after the God Alliance fight. The issue is which will come first, since its already been shown that Issei will be playing Sona.

Also, I feel most people think Rose is going to get engaged first because Helmwige was a around Zen and Shin's age, and Shirayuki and Kurobara were 1 year younger. But another thing to realize here is that Rose is more able to have children than Koneko, so, even if Koneko is engaged and married before Rose, she couldn't necessarily have children as soon as Rose could. Besides, we've already thrown out the age thing with Rias and Ex, and we know that was because Rias, as a pureblood, was harder to get pregnant than the other girls. In addition, Koneko and Kuroka obvious had a threesome will Issei when they got pregnant, since the sisters are the same exact age down to the day. This would mean either Kuroka waited until Koneko could do it, or she just happened to get lucky when Koneko did.