I saw the ad for this on TV at the beginning of the week, and since they weren't showing the actual burger (clearly), I guessed that it might be the black coloured bread that I've seen in Japan.... and sure enough, it was. (which is why they don't show it on the TV commercial, as it might put people off, rather than tease them into finding out what it is)

The advertisement at the store...


And what one looks like for real...
The box has the Colonel on it, but only when the light shines on it in a certain way.


Inside the lid is the list of ingredients. (the black coloured bread is traditionally coloured by adding bamboo ash to the dough, but I don't know if they did that with these)


Mine had a big finger mark on the top, as it must have been handled fairly roughly.

.

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The bread didn't taste any different, and with the chilli flakes, it had a real bite to it. But the mustard & maple sauce gave it a big sweet taste to it, clashing with the chilli.
Probably worth trying just to say that you've eaten black bread, but not worth buying again.