Miso Katsu Mistake!!

So last weekend was a long weekend, so my wife and I took the opportunity to get out of the city for a bit and went 300kms down the road to another smaller city called Hakodate. We actually stayed about 40kms north of it or so in a nicely maintained free campsite on the side of a beautiful lake called Onuma. Well actually, for the first couple of days we wouldn't have known that the lake existed really for the terrible storms we were having. Hokkaido was just experiencing the tail end of a typhoon, which had just passed the rest of Japan that week. Did a little bit of rain (read about 40 odd hours straight) and a few days of strong wind stop us from going out camping, not if you've ever met my wife when she's got in her head that she wants to do something.
Anyway, it all turned out pretty fun, cos we set up the back of our station wagon car as a big cushy bed and flipped open the laptop to watch movies and a few episodes of Samurai Jack (cartoon that I'm just getting into and really enjoying). You may say that that is no different to what we could've done at home, but that doesn't take into account the uniqueness factor of sleeping under a metal roof with the rain pounding down. I had one of the best sleeps in a long time.
To make a long story short, and get to the good bit, the next night we were strolling around Hakodate under umbrellas when we came upon a 'Hokkaido famous' burger and pizza joint called 'Lucky Pierrot'. It sounded pretty good so we walked in to order. The styling looked like something a little out of the movie Grease, like an old American diner that I've only seen in movies. I glanced quickly at the menu and ordered the miso katsu burger, which was a bit of a strange choice for a burger shop, but if you've ever tried a good piece of tonkatsu (like schnitzel, but juicier and is crumbed differently) you'd understand why. Well I bit into said burger, and was immediately surprised by the slightly odd taste and colour of the meat. The meat colour was a dark grey, but not the usual shade of beef or anything that I'd ever seen. Then my wife mentions that on the menu they also sell pieces of black chicken (whatever that is), so I figure that the store must have some sort of marinade and this changes the colour of the meat and gives it a strange taste, also a chicken katsu is not at all unusual. At my comments about the burger my wife takes a bite, and the puzzled look on her face shows that she remembers the taste and has had some of this meat before. Not too long after that when my burger was all eaten, she looks down at the menu again, looks up at me with a big grin and asks 'so how did you like your first WHALE burger!?!'
Bugger!