Debt bankers and investors are bracing for what is shaping up to be the next big trend in the global credit market: Japan Inc. raising billions abroad.

A string of recent megadeals is setting the tone. A giant sale by telecom giant NTT has already driven Japanese nonfinancial corporate issuance in euros and dollars to a record this year, based on data compiled by Bloomberg. One Morgan Stanley banker in London has even come up with a nickname for such bonds: reverse Samurai.

Japanese companies are heading overseas to borrow as their local market is becoming too volatile and rates are rising. They are finding there is buoyant demand for credit among dollar and euro investors in much deeper and more stable pools of capital.