User blog comment:B214/High School DxD EX/@comment-25262334-20150724215538/@comment-3965848-20150725062331

hard to say so because Rias and Sona were men't to have a Rating Game which would have happened naturally in the anime if Loki didn't interfered at moment in V5.

Plus the event's between LN and anime have slightly different since S1, I'd say history was branched in two when Issei activated his BG on the street (anime) instead of within the clubroom early on (LN).