I was at a hotel breakfast buffet in Hokkaido on Xmas Day when this English lady waltzed in and started going around saying Merry Christmas to all the employees and handing each of them something (some type of gift) in a highly public manner. I don't know how folks feel about visitors pulling off stuff like that in Jpn. Anyways, this is an aside as I know the OP is interested in doing something discreetly.