User blog comment:B214/Question and Answers/@comment-162.202.198.72-20130810084741/@comment-1359322-20130811010355

It'll never have any sex scenes in it. Issei was originally supposed to suck Rias' breast to attain his Balance Breaker but Fujimi Shobo didn't allow it, so it instead became Issei pressing Rias' nipple to power up.