Nippon Life, Japan Post Insurance and Sumitomo Life are among the insurers that have detailed their investment plans for the rest of the fiscal year-ending April at briefings over the past several days.

A common theme has been an intention to increase holdings of the longest-maturity JGBs, centered on the 30-year securities, which now offer "attractive" yields as well as being a safe haven from a long list of market uncertainties globally.

Many insurers also plan to shift some money from currency-hedged holdings of foreign bonds into yen bonds, with hedging costs soaring.

"There is now an attractiveness to Japanese government bonds," while "the attractiveness of hedged foreign bonds is waning," a Japan Post Insurance representative told a briefing on Friday. "We have already been shifting from hedged foreign bonds into JGBs, and we will continue to do so."

Yields on 30-year JGBs soared as high as 1.685% on Thursday for the first time since September 2014, while the 20-year yield reached the highest since February 2015 at 1.315%. Both fell back as investors scooped up the discounted debt.

Yields came under further downward pressure on Wednesday amid a decline in U.S. yields and as the Bank of Japan bought additional bonds ahead of a two-day policy-setting meeting that begins Thursday.

The 30-year bond last yielded 1.54% with the 20-year at 1.18%.

"Anything above 1.5% and we can consider additional investment" in 30-year JGBs, said a representative from Sumitomo Life at a briefing on Tuesday.

Nippon Life is being more cautious.

"It's true that it's the easiest environment to invest for the past several years," a representative of the company, also known as Nissay, said on Monday. "Because yields are at 1.5%, if the question is whether we can now buy actively, we're still a long way from that point."

(Reporting by Tomo Uetake and Tokyo markets team; Writing by Kevin Buckland; Editing by Mike Harrison)

By Kevin Buckland and Tomo Uetake