When you first came to Japan, you might be surprised that the car is running on the left side of the road. This is British style. Although Japan has never been a British colony, it was strongly influenced by the UK on modernization that began about 150 years ago.
Also, the old samurai had a rule to walk on the left side of the road. Because they had a sword on the left side of the body. Therefore, it was necessary to avoid hitting each other’s sword when passing each other. Perhaps this custom was adopted for car traffic.