Interesting development, that Yahoo have not done elsewhere.  They have tended to partner in other countries, but Yahoo Japan does operate under a different model.

Finextra: Yahoo Japan confirms net banking stake

Yahoo Japan confirms net banking stake
Yahoo Japan has confirmed that it is buying a stake in Japan Net Bank, the online banking subsidiary of Sumitomo Mitsui Financial Group. Financial terms of the deal were not disclosed.

Under the deal Yahoo will acquire 14.9% of a new holding company for Japan Net Bank. Sumitomo Mitsui’s core commercial banking unit will transfer its 57% stake in Japan Net Bank to the new holding company, which is expected to be established by September.

Yahoo says it may raise its stake in the holding company to as much as 50% in the future.

The deal with Sumitomo Mitsui will expand the banking and settlement services available to users of Yahoo’s online shopping and auction sites.