Even in North America, houses are considered a depreciating asset. The property on which the house sits is what tends to appreciate, hopefully offsetting the losses on the house (at least from the owner's point of view).
But with negative population growth and virtual no immigration as is the case with Japan, fewer properties are needed to sustain the decreasing number of people. Supply exceeds demand, so prices fall.
But I'm not sure how much you can conclude from that as a condo could still appreciate (i.e. someone would be willing to spend more money for it) even if the underlying physical plant were deteriorating at some rate. It's probably also worth noting that, in a lot of cases in the US, single family homes in particular don't necessarily deteriorate. People do maintenance, redo their kitchens, add decks, etc.
As a condo owner, you also own a representative share of the land the condo is built on (not an actual plot, but an interest in the total value of the land). The condo can depreciate, but if the land appreciates, the overall value of your share can appreciate.
But with negative population growth and virtual no immigration as is the case with Japan, fewer properties are needed to sustain the decreasing number of people. Supply exceeds demand, so prices fall.