If the Bank of Japan wonders why its monetary magic is gone, officials can find answers in the battle over Sharp.

On Jan. 29, Bank of Japan Gov. Haruhiko Kuroda tapped his wand and conjured up yet another surprise. At first, Kuroda's trick involving negative interest rates worked wonders as the Nikkei soared and the yen plunged. A week later, it's clear Kuroda's spell has fallen flat. Why? Investors are looking behind the curtain and disenchanted by who's really managing the show: a ghostly corporate sector.

Sharp alone dispels the notion of an ascendant Japan. Sure, the electronics giant may get a happy ending. Word is, Sharp may accept a takeover bid from Taiwan's Foxconn, and that's a good thing. But the way this deal came about is emblematic of why the BOJ's sorcery isn't what it used to be.