あけおめ! (a-ké-o-mé) “Happy New Year!”

To wish someone “Happy New Year” in Japanese, say: あけましておめでとうございます！ (a-ké-ma-shi-té o-mé-dé-tō go-zai-masu)

Or, more casually, take the first 2 syllables from each word and say: あけおめ！ (a-ké-o-mé)