Perhaps due to the rapid and dramatic economy change of Japanese burst of bubble in 90's, there must have been a huge change of social value system such as; the collapse of lifetime employment security with same company and the wide spreading and cost-cutting of part-time contract job with lesser staff benefits, because so many merging of corporation across in so many business sector.
I think this phenomena is not unique to Japan but also happening in those leading well-developed economy countries as well. Since the majority of these new Japanese generation are still mostly taken care by family (living together with parents), there are no urgency or desire to work so hard or strike for the best to pursue the dream of individualism due to the reality of tough available social job opportunity and upward mobility plus the existing living standard are already comfortable enough.
Perhaps the extremely low birth rate but seriously ageing society are also shaping their society to a kind of hopeless and lesser unnecessary desire of struggle for a better life indeed.