Most Japanese ice cream bars are pretty much throw-away material, except for those from the super-premium brands like Ben & Jerry's and Haagen Dzas, but they usually cost upwards of 300 yen for a couple of small bites -- not worth it when you can get a superb slice of cake or other freshly made dessert in a top-line Tokyo coffee shop for about 450 yen.
But along comes LE CHOCOLAT DES CHOCOLAT from Akagi for 100 yen (about 90 cents US). I bought one on a whim today and it was intensely chocolatey, with good cocoa flavor, and an amazingly creamy, fudgy texture. And this isn't even ice cream -- technically it's "ice milk."
What you get is this frozen pudding/fudge-like material that is close to black, and said to contain chocolate biscuit crumbs. There is a very high cocoa content, it seems, so your theobroma meter will go into the red. Then, this is coated with a dark chocolate with a high cocoa content. Other ingredients of note are cinnamon (barely perceptable) and soybean (I wonder why, maybe lecithin?).
It is awesomely chowlicious, and thoroughly unpretentious. 100 yen! And it really made my Sunday.
I found mine in a 7-Eleven, so convenience stores are a good place to look for this.