By Asahi Shimbun’s report [J], I came to know this Japan version of the famous internet prank had been planned.
It is not a subway but a JR Yamate line train, on January 10th Sugamo police department had caught the information that there would be “No Pants Subway Ride” held. They sent 60 police officers including chief commander of the department.
The police commented to Asahi, “Promoting unnecessary social confusion must not be allowed”.
It was hard to find at where people called for the prank in Japanese, but it turns out to be led mainly by residents foreigners on an English social network Facebook. And if so, probably it is the same situation as Yamate Haloween train which caused web discussions among expatriates and some 2-channelers, on which 2-channel users reported to police to stop it.
See Also:
A blogger kachupunk’s report [J]
Sankei also reports but emphasizes on New York’s successful one [J]