Driving on the Left
In Japan, traffic runs on the left side of the road, and cars have their steering wheel on the right. This puts Japan among the minority of nations worldwide, since most countries drive on the right.
A British Connection
Japan was never part of the British Empire, so its left-side driving has a more roundabout origin. In the late nineteenth century, as Japan modernised, British engineers were hired to help build the countrys first railways. They built the rail network to run on the left, following British practice. As roads and motor traffic developed afterward, they naturally followed the same left-side pattern the railways had set.
An Older Habit
Some historians trace the preference back even further, to the era of the samurai. Samurai wore their swords on the left side, and keeping to the left of a path reduced the chance of swords clashing as two warriors passed. Whatever the deepest root, left-side travel became official Japanese law in the 1920s. One curious exception existed for a time: the island of Okinawa drove on the right while under American administration after the Second World War, and only switched back to the left in 1978.
Source
This article was written using information from Wikipedia.