User blog comment:DeathGodPrayer/Talk About What You Want!/@comment-180.247.117.13-20121007080903/@comment-70.185.106.19-20121008093425

from what i can remember volume 10 life 1 it was right after issei and rias met venerana and milkas at the show they were doing, during the fight at the end of the show about how far rias and issei have gone before she begins to talk to issei she askes rias if she had decided on the sequential order of his harem

hope this helps wont give any spoilers and sorry if i mispelled any of the names