"There's the possibility the market is looking forward to tapering in the U.S., however uncertain that may be. (Tapering) argues for further weakness in the yen over the medium term. There are reasons for the dollar-yen to go up," he added.
Weak yen, strong Nikkei
Japan's Finance Minister Taro Aso was on Thursday quoted as saying that it was important to keep currency intervention as a policy option to prevent one-sided moves.
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Analysts said the remarks may also be contributing to yen weakness, and the Nikkei's bounce.
"Such words should do little more than help investors feel confident that Japan would prevent a deep fall in dollar-yen, perhaps as far as below 95. But at some level it may help encourage investors to increase their exposure to short yen positions," Gibbs said in separate note.
The Nikkei, the best performing major stock market globally so far this year, may also be getting a boost from expectations that an economic recovery may stick this time.
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"Given the depreciation of the yen and an economic recovery, companies are likely to run down their savings for use in forward-looking activity (capex and employment). Corporate savings are set to fall further, thus accelerating the domestic demand recovery and the easing of deflation," Societe Generale said in a report published earlier this week.
"Total leverage is growing," it said. "As total leverage expands further, the yen is likely to depreciate further on the back of a steady U.S. recovery," Societe Generale added. "The Japanese economy has just entered a virtuous economic cycle for the first time in more than a decade."
— By CNBC's Leslie Shaffer. Follow her on Twitter: @LeslieShaffer1