User blog comment:B214/Question and Answers 6/@comment-24098614-20161119184223/@comment-26821288-20161119221310

Threesome was probably the case with Koneko and Kuroka (I mean, their children were born at the same day. It might be some kind of a hint for us, although it doesn't make it so absolutely), so maybe Akeno would also be okay with it. I think Akeno might even be all for it, because she has her M side, and she really is in for having an affair with Issei, and threesome can be seen as something quite close to it. Although it's just my opinion.