Tokyo police are on increased alert as young people and foreign nationals in Halloween costumes descend on the city's busy Shibuya district.
Areas around Shibuya railway station are crowded with revelers in gruesome horror make-up and anime costumes.
The police have deployed riot squads to prevent accidents.
At the famed scramble crossing near the station, a special public relations unit known as the "DJ police" is using loudspeakers to tell pedestrians in Japanese and English not to pause for pictures in the middle of the street.
The police have been patrolling the city's main entertainment districts since Friday. They say that no major trouble has been reported so far.
The police will remain on the alert and remind revelers to obey traffic rules and display good manners.