User blog comment:Crimson and Darkness/Volume 25 discussion blog/@comment-83.49.74.12-20180512132507/@comment-34891930-20180512134834

Heavenly breasts that were mentioned during talk with chichigami were- Rias,akeno,asia,kuroka,koneko,Irina,xenobia And most probably or either basically confirmed are- Rossweisse,ravel,elmenhilde,lefray,kunou So basically heavenly breasts are one whom Issei have proposed but limited to first 12 wives.

Now you must be thinking why rossweisse is not included.. it's because Issei conversation with chichigami was prior to the match:)