Japanese joggers are being warned to mind their manners when they run around the Imperial Palace in central Tokyo, after a spate of rudeness.
Officials say tourists and older visitors to the grounds have complained of runners crashing into them from behind and then trotting off without saying sorry.
"In some cases, the victims were jeered at or yelled at by joggers," said an official from Chiyoda-ku, the ward in Tokyo that is home to the palace.
While the emperor's official residence is strictly off-limits, large parts of its sprawling grounds are open and provide a welcome green lung in densely-concreted Tokyo, attracting around 10,000 runners every day.
Chiyoda-ku officials, who say they have received around 100 complaints in the last three-to-four years, have now erected signs urging joggers to observe the rules: yield to pedestrians, run counter-clockwise and be polite.
Japan's strict codes of behavioural conduct, which govern everything from riding the subway to using a public bath, are routinely reinforced by signs or noticeboards filled with do's and don'ts.
While some older Japanese bemoan slipping standards of behaviour, public confrontations and outright rudeness remain very rare, even in densely populated Tokyo.