As an American living in Japan for a year, I expected the apartments to be smaller. What I didn't expect were the functional design differences in living styles. Three things in particular took some getting used to: 1) Having to constantly remember to turn the apartment's gas off when not in use (due to earthquakes), 2) washing machines but no dryers (due to expensive electricity), and 3) the bathroom designs (due to different views on ablutions and elimination).
The bathroom in my apartment was like everyone else's there: Completely waterproof, like it was in an RV. As space-tight as the apartment was, the toilet was off in its own little room and had a sink built into the top of it, like they have in American jails. The sink faucet was on a pivot and also served as the bathtub faucet. And on and on.
To get a good sense of how Japan's distinct view of bathrooms influences their design, watch this little girl run down the design features: