  We present Subaru observations of the newly discovered luminous quasar AKARI
J1757+5907, which shows an absorption outflow in its spectrum. The absorption
consists of 9 distinct troughs, and our analysis focuses on the troughs at ~
-1000$ km s^{-1} for which we can measure accurate column densities of He I*,
Fe II and Mg II. We use photoionization models to constrain the ionization
parameter, total hydrogen column density, and the number density of the
outflowing gas. These constraints yield lower limits for the distance, mass
flow rate and kinetic luminosity for the outflow of 3.7 kpc, 70 M_{sun}
yr^{-1}, and 2.0 x 10^{43} ergs s^{-1}, respectively. Such mass flow rate value
can contribute significantly to the metal enrichment of the intra-cluster
medium. We find that this moderate velocity outflow is similar to those
recently discovered in massive post-starburst galaxies. Finally, we describe
the scientific potential of future observations targeting this object.
