あけましておめでとう | akemashite omedetō | happy new year NB: Akemashite omedeto (あけましておめでとう) should only be said once the new year has began, on New Year’s Eve the right expression to wish a Happy New Year is yoi otoshi wo (よいおとしを)!
When I lived in Tokyo I took up the Japanese tradition of sending a new year zodiac animal postcard. 2018 is the year of the dog. This dog is based on an Inu Hariko (lucky dog toys that are the protectors of children and pregnant women). The bottom left says 2018 (in a special year numbering system) and the character below it is the special character for dog used only for year of the dog. On the top left it basically says Happy New Year.