  We present the result of the Infrared Medium-deep Survey (IMS) $z\sim6$
quasar survey, using the combination of the IMS near-infrared images and the
Canada-France-Hawaii Telescope Legacy Survey (CFHTLS) optical images. The
traditional color-selection method results in 25 quasar candidates over $86$
deg$^{2}$. We introduce the corrected Akaike Information Criterion (AICc) with
the high-redshift quasar and late-type star models to prioritize the candidates
efficiently. Among the color-selected candidates, seven plausible candidates
finally passed the AICc selection of which three are known quasars at $z\sim6$.
The follow-up spectroscopic observations for the remaining four candidates were
carried out, and we confirmed that two out of four are $z\sim6$ quasars. With
this complete sample, we revisited the quasar space density at $z\sim6$ down to
$M_{1450}\sim-23.5$ mag. Our result supports the low quasar space density at
the luminosity where the quasar's ultraviolet ionizing emissivity peaks,
favoring a minor contribution of quasars to the cosmic reionization.
