TOKYO—A week after Japan's central bank started a huge bond-
buying campaign to drive down yields in the country's
quadrillion-yen government-bond market, yields instead have
risen, a sign of the huge headwinds the bank faces in its push
to end 15 years of deflation.  The rise is puzzling because it
comes after the Bank of Japan pledged to double its Japanese
government-bond holdings to ¥190 trillion ($1.93 trillion) in
two years, the centerpiece of an aggressive new monetary-easing
push aimed at stimulating investment, spending and prices. In
theory, such a huge increase in purchases should cause bond
prices to rise and yields to fall.  The April 4 Bank of Japan
policy-board meeting that set the more aggressive bond-buying
plan in motion Agence France-Presse/Getty Images  The rise in
yields also puts the bond market out of sync with currency and
stock markets, which have reacted enthusiastically to the bank's
campaign. Shares have soared and the yen has weakened since the
bank unveiled its plan on April 4, in