Japan is apparently a very unhappy place. In a Discover report on a recent study, Japan is ranked 90th:
"Japan's ranking (90th) was surprisingly low given its high scores for health, wealth, and education. White suspects cultural factors may be at work. Some researchers speculate that a focus on competition and a tendency to downplay enjoyment may contribute to low reported happiness among some Asian cultures."
Denmark is ranked 1st. Iceland is ranked 4th which is not surprising giving its 'party culture' too.