User blog comment:B214/Question and Answers 6/@comment-24098614-20190617190922/@comment-38340421-20190711195453

All of Issei future waifus will grow in size. It was mostly explained by Ravel. It's not just because of their dna. Some of it is a factor, but not the main factor. The others are devil aura and what their potential mate wants. I think it was even stated by one of the future kids that they don't understand anyone liking flat chested women or something along the lines. Which means all of the waifus are quite busty in the future. Give it time and all will be quite big. ;) Although they all still have quite a bit of catch up to do comparing to Yasaka. lol