In the U.S., 7/Eleven is one of many convenience-store chains. In Japan, it's an iconic retailing powerhouse — and it has owned 7-Eleven in the U.S. for 18 years.

Another model: The Seagate-Veritas deal. Seagate, a hard-drive maker, owned a large chunk of Veritas, a storage-software company it had spun off. In a $20 billion deal, Silver Lake took Seagate private, swapping out Seagate shares for Veritas shares. Similarly, Yahoo Japan could unlock its shares held by Yahoo by swapping them for a large equity stake. Complicated, but not inconceivable, especially if private equity injects some cash — and money managers might be keener on a direct stake in Yahoo Japan than in the U.S. operation.

The key to such a deal would be Softbank, which owns 41 percent of Yahoo Japan. Softbank CEO Masayoshi Son has close ties to both Microsoft chairman Bill Gates and Yahoo CEO Jerry Yang, who sits on the board of Yahoo Japan.

Softbank also owns 3.9 percent of Yahoo, but it also owns, as does Yahoo, a large stake in Alibaba, the operator of Yahoo China. Alibaba's management is reportedly restive about the prospect of Microsoft getting a say in their affairs. Softbank might throw its Alibaba stake into the combination, which would give Alibaba an exit in the public markets without the risk of an IPO, and the new Yahoo majority control of its Chinese websites.

Making the numbers work, especially when Microsoft could easily raise its bid, is a challenge. In some ways, selling out to Yahoo Japan would be as humbling to Yahoo's management as selling to Microsoft. But while Tokyo is more distant than Redmond, I suspect the cultures are more compatible.

The fundamental logic of Microsoft's bid is that it can do more with the Yahoo brand than Yahoo itself can. Many doubt Microsoft will actually manage that. Yahoo Japan has proven it can.

This chart from search-engine marketer Efficient Frontier shows, outside the U.S., Yahoo is a financial nonentity. Japan, the exception, does not count: Yahoo Japan is separately traded, and not part of Microsoft's offer. $44.6 billion for a company which will not substantively improve Microsoft's market share in search advertising. This is an Excel bug I have yet to hear about.

Yahoo Japan, of which Yahoo owns a third, is worth $25 billion, putting Yahoo's stake in it at nearly $9 billion. Alibaba.com, a Chinese e-commerce company in which Yahoo directly owns a 10 percent stake, is worth $17 billion. Tack another $1.7 billion on. That figure doesn't include Alibaba.com's parent company, Alibaba Group, which runs Yahoo China and in which Yahoo owns a currently illliquid 40 percent stake. Estimates of its value are running between $8 billion and $16 billion. Yahoo has other investments like G-Market. Add it up, and you realize that Yahoo's wholly owned operations in America and Europe are valued by the market at next to nothing, especially compared to the multiples other Web companies are getting.

Good thing Yahoo president Sue Decker has a Wall Street background, because at this rate, she might as well be running a mutual fund.