There are a lot of western (mostly French) cake shops everywhere in Japan.  Some cake shops sell more delicate and sophisticated concoctions, and others simpler, everyday snack types.  Wherever you go, though, you will definitely find Purin (プリン) in most shops in Japan.  There are often millions of new cakes and other desserts to choose from there, but people always come back to something they ate in childhood.  Purin is exactly like that.  It is a comfort dessert for Japanese people.