The English-speaking manager at the Peacock supermarket where I shop told me this was a highly regarded plum wine, but the fruit on the carton looks suspiciously like apples. Whatever, all I know is that this "traditional Japanese fruit liqueur" is quite good, if you like that sort of thing. In restaurants I've seen it served with a golf ball size hunk of ice, but I'm taking mine straight-up, baby. (That's our Toshiba microwave in the background.)
UPDATE 1/23: okay so here's what I learned by doing 30 seconds of online research: umeshu (plum wine) is made by steeping still-green ume (a type of Asian plum) in sugar and shochu (a distilled alcoholic beverage) so that explains why the fruit on the box is green. Mystery solved.