First of all, yes, people in Japan spend Christmas quite differently than people in the United States. The most unique thing about Japan's Christmas is that Japanese people love eating KFC on the 24th.
Every Christmas season, an estimated amount of 3.6 million people purchase fried chicken buckets. KFC Japan's busiest day is usually December 24, selling about ten times more than on typical days. Since it's so busy, people in Japan must make reservations for pickup by December 19, even to purchase KFC on the 24th.
It all began in 1974, when Takeshi Okawara, the manager of the first KFC in Japan, started a marketing plan nationally, calling it Kentucky for Christmas. During this time, KFC specializes in selling "Party Barrels" for Christmas. Japan never had a Christmas tradition, so it filled a void for the Japanese people. So, thanks to her, it has now become a nationwide tradition.
https://www.afpbb.com/articles/-/3444822
https://news.livedoor.com/article/detail/17331006/
In Japan, New Year's is the most important holiday of all. Japanese New Year is called Oshōgatsu (お正月) in Japanese. The Japanese people typically spend time with their family and loved ones while eating lots of traditional food and praying for good fortune. Japanese families gather and participate in various traditional and cultural activities.
My favorite thing during the New Year's was eating Mochi with the fam! Sticky rice cake (Mochi) is a special holiday food, and it is a common tradition to make Mochi by hand. Traditionally, Mochi is made by pounding steamed short-grain Japanese sticky rice (called mochigome), with a wooden mallet. This allows the rice to pulverize and creates a sticky and beautiful texture.
https://gigazine.net/news/20160617-fastest-mochi-maker/
https://www.otafukumochi.jp/info/1199/