The Tokyo Metropolitan Police put up metal fences along the sidewalks, roadblocks, and restricted access to areas in the "protest zone" that they had set up, and effectively divided the protest into small pieces. No one seems to know how many people showed up.
The supposed "police" number quoted by the press is 10,000 people, though the PR department of the Tokyo Metropolitan Police has said they don't announce the numbers. What "police" the mainstream media outlets have been quoting, no one knows; supposedly some anonymous inside source that the press club reporters have access to all the time.
So, it was a success for the Noda administration and the pro-administration media, who didn't need to quote the number from the organizers this time.
This photo from the article by independent journalist Ryusaku Tanaka (7/13/2012) shows the police on one side of the metal fence and protesters on the other side. An older man on the left, looking at the camera looks puzzled and annoyed. (Click to enlarge.)
Tanaka calls it "Intifada". In Japan, it usually means the Palestinian ones. That's how he describes the protest that is herded in by the metal fences and the law enforcement.
In his article, Tanaka quotes two protest participants, both women in their 50s. The first one speaks like a man:
"Stop bullshitting me. Citizens gather here to express their wills, and what's the point of this metal fence? With this many people coming, they should just open the road." (a woman in her 50s from Nakano-ku, Tokyo)
"I'm here for the first time, and there are these metal fences. I'm surprised at this elaborate security. I want to raise children who can say "No". Before I came here today, I explained to my students why I was not giving lessons today." (a woman in her 50s from Nagoya, who runs a private music school)
There are tweets from younger people saying they didn't like the "obnoxious and impolite" baby-boomer generation at the protest, who apparently complained loudly to the police and to the pushy cameramen from the media, as they should. Well, young people, tough.