Why do Japanese drive on the left?

It's been warm these days...above 70. At the end of the day, a long hot bath with a cool refreshing treat to follow is THE best. For example, I had this white peach jelly.

Warm spring nights in Aobadai.

One of my friends explained to me the reason why Japanese drive on the left side of the road. Long time ago during the time of Samurai, they would keep their swords on their left side. Therefore, they would pass other samurai on the left also. It was easier to draw your sword if you were to be attacked by another samurai. cool huh?