EDIT! As is the way with some restaurants with a bafflingly convoluted concept and not the greatest menu in the world. Half Dime is gone now - flattened in fact - bulldozed to the ground to make way for something infinitely less awesome than a steak restaurant staffed by post apocalyptic miners named Mermaid.
So we were driving back from Tomakomai in the dark, in the rain and I fell asleep in the car. When I woke up we were back in the outskirts of Sapporo, but it was night so I had no idea where we were. Yuki asked where I wanted to eat, and suggested Italian, which sounded good, but suddenly we seemed to be approaching some kind of densely forrested mountain:
Is that a restaurant? I asked, still half asleep. Yes, she said, the same one that you took pictures of closed down near the freeway. Wait, so are we in the past now? I thought, but luckily we weren't so we went there to eat.
I didn't take pictures inside because it's so incredibly dark I doubt they would have come out. For a long time I thought I was still asleep too because the place was so unreal. The waiters wore kind of Peter Pan rags and face paint. Our waitress took us to our table, I was half asleep so I didn't listen to what she said, Yuki whispered to me: "She's Mermaid". Nothing was making any sense, so I looked at her costume, which didn't resemble a mermaid one bit. "No, her name. She said her name is Mermaid." It made as much sense as anything.
It turns out that the concept of the restaurant is that it's a MINE, and they serve roast beef and choice meat cuts. The menu was severely lacking in choices to be honest, and was kinda pricey, but when the food arrived it was great. That said, I certainly wouldn't recommend it on the strength of that, but for the whole experience... it was really something. It was late at night when we went, and the place was deserted, and inside it's huge and labyrinthine, so we sat at a booth in a curved passage and couldn't see a single other diner from where we were. I'm not sure how the face paint and fantasy names fits into the Mine theme, but possibly they used to be miners but they became trapped underground and developed their own society... that would make sense. As much as anything does. They had a gift shop full of utter junk, generally themed around dinosaurs, jewels and statues that their "Miner King" had found.
I'm going to try and mark the place on my Sapporo map, but I really have no idea where it was - possibly you have to still be dreaming to access the dimension on which it rests.
EDIT! Well, it does exist, and can even be seen on google street view (marked on my map of course), althought it looks half the size it did in the dark. There's even some info on the Hokkaido Gourmet Navigator that says that it's: "based on the idea of an underground shelter in the 49th century world that has terribly ruined after 3000 long years. Our staff wear moor than 30 types of "character uniform," and we have lots of fun with magic, fortune-telling, parades of a musical troop and more!" We didn't get magic tricks, but it's probably for the best. At that point I would have totally lost my mind.