So the Prismrivers stay in Hakugyokorou for this continuity. Or maybe they're just visiting.
They're next-door neighbors in canon, aren't they?
After you beat up the Prismriver sisters for no good reason in PCB, they tell you that Yuyuko lives (okay, "lives" might not be the best word here, but you get the picture) right on the other side of the barrier. The barrier's locked and they don't have the key, but the heroines are told to simply fly over it.