(1) The structure of the sub-prime crisis and financialization of labour-power: The sub-prime crisis originated from the US bubbly housing boom which lasted for ten years until 2006, and expanded to a world crisis. The preceding boom was promoted by speculative housing finance. About 43% of the total US households are estimated to have obtained homes by housing loan. The subprime housing loan was for people mostly of relatively lower income without sufficient creditability. Thus, commoditized labour-power became more and more broadly financialized in our age. The structure of US housing loan was double-decked in this period. At the first floor, mainly mortgage companies lent housing loan to households, and immediately sold housing loan credit to other financial institutions such as SPV (Special Purpose Vehicles) which was owned by big investment banks. Then at the second floor, SPV and parent banks bundled and re-composed such individual housing loans into mortgage backed securities (MBS) and other forms of securities, and sold them in a world market. Through this double decked financial market, global idle money was continuously poured into the US speculative housing boom. (2) Expansion of the sub-prime financial crisis to the world crisis: Corresponding to the double decked structure of the US housing finance, the collapse of the speculative housing boom in the USA spread destructive impacts to the US and the global economy in two aspects. Firstly, as the boom was promoted by speculative trading in financial business, deterioration of sub-prime and other housing loan based securities like MBS hit badly both US and world-wide banks and other financial institutions. The financial crisis enforced widely to depress business activity and consumer demand. Secondly, so long as the US consumption was much expanded by housing related expenditure, the collapse of housing boom itself devastated the US real economy. (1)The impact of financial crisis, (2)a decline of export, (3)the chained collapses of similar real estate booms in some countries, are main routes or types of contagion of economic crisis in the world. The Japanese economy suffered much from the second, in relation to domestic economic problems, though not much from the first route this time. (3) How to apply Marxian crisis theories: Against neo-classical economics, Marxian political economy is well equipped with basic theories of economic crisis. An attempt is shown here to apply Marx's over-accumulation theory of crisis to the sub-prime crisis, by emphasizing also Marx's and Uno's theoretical contributions to the theory of monetary and financial instability. (4) Social costs of the sub-prime crisis: Neo-liberalism was grounded upon the neo-classical micro-economics, and asserted that a competitive and deregulated market can realize most efficient waste-less economies. The result of its dominance for about three decades in the leading economies should be seriously criticized in view of waste-full social costs of the subprime crisis in four forms. What to think about the capital loss among them from the view of labour-theory of value is presented as a theoretical issue to be reconsidered. (5) The end of neo-liberalism for social democracy and socialism: The sub-prime crisis signified the historical limitation of neo-liberalism and actually worked as an epoch to end the neo-liberal regime. Both Obama Democrat and Hatoyama Democtat administration were born in 2009, demonstrating people's choice for such a change. A wider room to argue for new possibilities of social democracy and socialism is now open as global agenda. The issues of green recovery and basic income are referred to as illustrations. The large-scaled once-a-century world crisis requests us revival of political economy concerning wider historical alternatives for the future.