Twenty is the age of adulthood in Japan, when a person is old enough to vote, drink or smoke.
Financial markets and many offices are closed for the holiday. Municipal governments host special coming of age ceremonies for the 20-year-olds in their juristictions. The ceremonies are held to encourage responsibility and self-reliance.
Young men usually wear suits to the ceremony. Young women usually wear special kimonos bought or rented for the event. - VOA News