The Bank of Japan's preferred inflation gauge fell for the second straight month in April, dropping from 0.9 percent in the previous month to 0.7 percent, as consumer prices refuse to cooperate with the BOJ's 2 percent inflation target, according to government data released Friday.

But the preferred price index — which excludes fresh food prices — was not the only measure to fall, as overall consumer prices also fell sharply, from 1.1 percent to 0.6 percent.

While market participants expect the drop to be temporary, with prices recovering in 2018, the persistent inability for inflation to gain upward momentum could further swing the monetary policy pendulum away from normalization. That idea was floated by Gov. Haruhiko Kuroda earlier this year, but was walked back over the course of the past few months.