User blog comment:B214/Talk About What You Want! 3/@comment-25009130-20160227042411/@comment-27876048-20160227070454

Well we all know at this point thanks to High School DXD Ex Le Fay and Elmenide (probaby spelled that wrong) will be in the harem. Then you gotta add Kuneo will probabily join when she is older and there's a chance for Kiyome Abe and Tsubasa. And finally you have take into account Issei's future peerage so best guess around 18 to 20 ladies in the harem.