Ooh, fascinating! It makes me wonder when the Ryudo family turned from 'we founded this temple on a leyline, and by the way the Holy Grail or whatever we're calling the magical artifact of power is in a cave under the temple' to 'we're not mages! We don't know anything about the Grail War! The witch living with us now can easily take over our bodies if she feels like!'. How the mighty have fallen...

Because Issei can never have too many things to flail over~