User blog comment:Jopjopjop/Volume 19 Spoilers/@comment-3965848-20150524093458/@comment-79.7.180.144-20150524232937

Even if Issei would pick up both Kunou and Yasaka it wouldn't be incest. He's not related with them. Yes, it would be strange, because if he makes babies with Yasaka and Kunou...then his sons and daughters (with Yasaka) would be even his brothers-in-law and sisters-in-law. And then his sons and daughters (with Kunou) would be even his grandsons-in-law and granddaughters-in-law. And he would be even the father-in-law of Kunou. So it would be a great mess, but not incest.