>It was actually a Koju and Aoi event
Really nice event. It's always good to see interactions between characters that never happened in the main story. From the looks of it, the event does take place before 5.1 and Higuchi's development

I gotta say though, despite how often she shows back up, this felt pretty definitive in tying up all the loose ends, but that's how it felt last time too. It's even established that Aoi left behind some evil horcruxes spread across the world (hyperbole) so she can always come back hahaha