Mochi – glutinous cakes of pounded rice – are traditionally eaten in vast quantities over the holidays, usually in soup, or toasted and served with sweet soy sauce and wrapped in dried seaweed.
Several people die eating the starchy delicacy every January, but this year the number is particularly high.
Local media reported that nine people had died in Japan over the holidays, while 13 others were in a serious condition in hospital.
Last year there were at least four deaths, compared to two in 2013.
More than 80% of such deaths occur among the elderly, who find it harder to swallow the sticky cakes.
Every year, Japan’s emergency services warn people to cut the mochi into bite-size pieces before serving them to young children or elderly relatives.
Amid fears that the mochi-related death toll will rise as Japan’s population continues to age, a firm in Osaka said it had developed easy-to-swallow mochi containing an enzyme that renders them less sticky.