Module 14.2 culture notes
Coming of Age Day (成人の日, Seijin no Hi) is annually held on the second Monday of January.
On this public holiday, young people who have turned 20 years old would attend Seijinshiki, a Japanese term that refers to the coming-of-age ceremony. 20 years old is considered the age of maturity in Japan.
During the Seijinshiki ceremony, young adults dress up in formal attire, usually traditional Japanese garments like kimonos for women or hakama for men. Local government offices would host Seijinshiki in the city halls, school gyms, or community centers to congratulate these young adults for reaching a new milestone in their life while stressing the responsibilities of adulthood.
After the ceremony, many families and friends would celebrate at a restaurant.
Sources:
https://web-japan.org/kidsweb/explore/calendar/january/seijinshiki.html
https://www.tokyoweekender.com/art_and_culture/japanese-culture/coming-of-age-day-in-japan/