User blog comment:Striker10/High School DxD BorN episode 7 review/@comment-108.168.36.205-20150517233019/@comment-26322543-20150518014411

Use recorded it in less than an afternoon in the LN. And Azazel said they'd record a song in episode 6, they could've done that between that episode and this one. The one responsible for the Oppai Dragon stuff seems to be Azazel, not Rias, they probably were invating him for the premiere of the tokusatsu show that no one of the ORC knows about at this point.