A bonen-kai is a party held sometime between the middle and the end of December every year. People gather to share and shake off the hardships they experienced during the past year, and to prepare for the coming year with renewed resolve. Usually parties are held among company colleagues or friends at restaurants and the participants enjoy drinking alcohol and eating delicious food. A bonen-kai is a concept unique to Japanese culture, but it is described in English as a year-end party, or you can just use the Japanese word, “bonen-kai,” as it is. 