Replying...
Intro. (Note this all takes place before cannon so Rias only has Akeno, Koneko, Kiba, Jasper as her peerage right now. Also while Riser knew of their impending marriage Rias was not informed till she decided to go to school in Japan its still not time for her to start school) Ravel had just earned her evil pieces she wanted desperately to celebrate and when her mother heard she called upon Venlana who talked Rias into taking Ravel up to experience the human realm Rias accepted and invited Sona and Seekvaria to come with after all what could go wrong.....

DXD Vegas mishap

@Imdamiller