Korean Christians celebrate Christmas similar to the way it's celebrated in the West, but since it's primarily a religious holiday in Korea, there is considerably less fanfare and presents. Some families do put up Christmas trees, people exchange presents, and stores do put up holiday decorations, but the festivities start much closer to Christmas day. Families may attend mass or a church service on Christmas Eve or Christmas day (or both), and caroling parties are popular for young Christians on Christmas Eve.
Grandpa Santa is popular with kids in Korea (Santa Harabujee) and he wears either a red or blue santa suit. Kids know him as a happy grandfather figure who gives out presents, and stores employ Santas to greet shoppers and hand out chocolate and candies. People in Korea usually exchange presents on Christmas Eve and instead of piles of presents, one present (or a gift of money) is customary.
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