The poster says “gura-kuro” (グラクロ). And what is “gura-kuro”? “Gura-tin kuro-ke”, i.e. a croquette filled with gratin cream, one of the most common Japanese snack foods. So much for American fast-food chains having diluted Japan’s gastronomical landscape.
(For a bigger version of this picture both in color and black and white, check my "Japan Arekore" set on Flickr)