  We investigate the net-baryon number fluctuations across the chiral phase
transition at finite density in the strong coupling and chiral limit. Mesonic
field fluctuations are taken into account by using the auxiliary field
Monte-Carlo method. We find that the higher-order cumulant ratios, $S\sigma$
and $\kappa\sigma^2$, show oscillatory behavior around the phase boundary at
$\mu/T\gtrsim 0.2$, and there exists the region where the higher-order cumulant
ratios are negative. The negative region of $\kappa\sigma^2$ is found to shrink
with increasing lattice size. This behavior agrees with the expectations from
the scaling analysis.
