Corporate governance reforms that have underpinned a nearly $2 trillion (¥308 trillion) rally in Japanese stocks are increasing the draw for investors in credit.

Japanese corporate dollar bonds have been outperforming U.S. peers, and borrowers have piled into the market with record issuance in recent months. Improved governance scores are helping to burnish the country’s credit at a time when the economy has finally shaken off decades of deflation,…