The Bank of Japan and a state money manager worked hand in hand last October with surprise easing and a portfolio reshuffle that boosted both stock and bond markets. This year, a similar one-two punch is not off the cards.

Japan Post Bank Co., which makes its stock-market debut five days after the BOJ policy meeting this Friday, may announce plans to boost holdings of shares as the central bank buys debt to fuel inflation, according to Amundi Asset Management, Resona Bank Ltd. and AMP Ltd.

The postal lender is the biggest holder of Japanese government bonds after the BOJ with 49.2 percent of its ¥206.5 trillion in assets in local sovereign debt and just ¥900 million in shares.