A friend and I talked about this just a few weeks after we got here, and we couldn't decide if it is a cultural thing, or just a result of this being such a crowded country.
Let's call it "Gaijin Gravity", AKA "the Suck Zone" or simply "the Vortex". It doesn't matter where you walk, on the left, on the right, in the middle, or hugging the wall, people walking opposite you will ALWAYS gravitate toward you. They get closer and closer, pretending they can't see the wall of flesh that is your fat American ass approaching them, yet moving into your path. I've actually had people come from the opposite side of the shopping arcade just to stop right in front of me with a look of surprise, like "Why are you blocking me?" Then you end up doing the dance macabre, jigging left and right, trying to find a way around each other, while they match you move for move. Of course, if you stop, you'll both bow in apology and bonk heads like the 3 Stooges. "I'm sorry. Ouch! I'm sorry. Ouch! I'm sor...."