User blog comment:B214/Light Novel Volume 16 spoilers/@comment-23853100-20131019035942/@comment-23853100-20131020012904

Well there's no really any reason to make all female characters that appear in the story fall in love with Issei. I mean he already has like: For the girls and: For the guys Either way, Issei already attracted so many girls and yet most of them has yet to have their relationship deepened or characters developed.
 * 1) Rias
 * 2) Asia
 * 3) Akeno
 * 4) Koneko
 * 5) Xenovia
 * 6) Irina
 * 7) Rossweisse
 * 8) Ravel
 * 9) Ophis
 * 10) Kunou
 * Abe
 * 1) Kuroka
 * 2) Le Fay
 * 3) Tsubasa
 * 4) Bennia
 * 1) Yuuto
 * 2) Gasper
 * 3) Vali
 * 4) Sairaorg
 * 5) Cao Cao