(Bloomberg) -- The Japanese unit of Massachusetts Mutual Life Insurance sold six times more bonds this year, shoring up capital as customers bought foreign currency policies amid a weakening yen.

The business sold $175 million of subordinated notes last month, adding to an inaugural $29 million sale in October that was the first such offering by a Japanese unit of an overseas insurer. The latest deal included perpetual securities with a 2.2% coupon. That compares with an average 0.5% yield for Samurai bonds sold by overseas companies and 0.31% for domestic corporate debt.

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