In Japan, most forms of gambling are generally banned by the Criminal Code chapter 23; however, there are several exceptions, including betting on horse racing and certain motor sports.
The bookmakers set their odds to make a profit whatever the outcome, the odds are based on money expected to be placed and statistical probability. Many OLBG member create their own betting odds before the bookies have priced up an event, it's a very worthwhile exercise and should become part of your betting life.