Kanchumimai (a winter greeting card) (寒中見舞い)
Kanchumimai (a winter greeting card) is one of the Japanese customs. It is the greeting card during mid-winter from Shokan (the second coldest day) in 24 divisions of the old calendar (around January 5) to Risshun (the first day of spring) in 24 divisions of the old calendar (around February 4).
Today, it means letters caring about others in a heavy snowfall area and a cold area. Kanchumimai is also used as a reply for nengajo (New Year's card) or a substitute for nengajo during the period of mourning.
In addition, it is used as an invitation to the seasonal rites and festivals, such as Setsubun (Demons Out, Fortune In).
Other than postcards, a return gift of an oseibo year-end gift could be sent too.