User blog comment:B214/Question and Answers 2/@comment-4547267-20140522190033/@comment-24098614-20140523013720

The friendship of Akeno and Rias is very special because if Akeno wasn't so close to Rias she could at any time try to steal away Issei from RIas if she wanted to, and trust me as beautiful and seductive as she is she would be very formidable against Rias but she cares for Rias to a point that she would leave Rias heartbroken if she did to her, and she owes Rias so much for saving her life as well.