I assume they fly in from all directions but sadly the area is all surrounded by tall buildings so it is very difficult to see the wider.
The birds fly towards the Chiba-chuo Station well before sunset in small flocks and wait on the aerials and fences on top of the buildings.
If you are a birder or you know what you're looking for, you'll hear their calls well before you actually see them. I was amazed when I heard them from several blocks away considering how noisy the city centre was.
As the sky got darker, they started to fly in flocks into the trees by the monorail and squabbling began everywhere!
The Grey Starling don't do murmurations like the Common Starling in the UK, at least, the ones in this area don't. If you are lucky (not lucky for the starlings, of course), a bird of prey or two follow the flocks, causing havoc among them. We were not so lucky on that day.