Coming-of-Age Day, also known as Seijin no Hi, is a significant annual holiday celebrated in Japan. It is held on the second Monday in January. The day is dedicated to young individuals who have turned or will be turning 20 years old within the current school year, marking their transition into adulthood. This age is particularly significant in Japan as it is associated with new rights and responsibilities; at 20, a person legally becomes an adult, gaining the right to vote, consume alcohol, and smoke.

The holiday is characterized by local city and town ward offices hosting ceremonies known as 'seijin-shiki'. The invitees, known as 'new adults', donned in formal traditional clothing, are congratulated by government officials and usually a guest speaker, often a popular celebrity. Women traditionally wear an elaborately colored and styled 'furisode', a type of kimono with dangling sleeves, while men often opt for a formal suit or occasionally a 'hakama', a traditional male outfit.

Beyond the official ceremonies, it's also customary on this day for the new adults to visit shrines and temples to pray for health and success. They often spend the day celebrating with family and friends. The holiday offers an opportunity for the new adults to show appreciation to their parents and those who supported their growth. Despite the serious undertones of adulthood, Coming-of-Age Day is generally filled with joy and celebration, and forms a colorful and vital part of Japan's cultural heritage.