  A southwest region of the Carina nebula was observed with the Suzaku
observatory for 47 ks in 2010 December. This region shows distinctively soft
X-ray emission in the Chandra campaign observations. Suzaku clearly detects the
diffuse emission above known foreground and background components between 0.4-5
keV at the surface brightness of 3.3x10^-14 erg s^{-1} arcmin^{-2}. The
spectrum requires two plasma emission components with kT~0.2 and 0.5 keV, which
suffer interstellar absorption of N_H~1.9x10^{21} cm^{-2}. Multiple absorption
models assuming two temperature plasmas at ionization equilibrium or
non-equilibrium are tested but there is no significant difference in terms of
chi^2/d.o.f.. These plasma temperatures are similar to those of the central and
eastern parts of the Carina nebula measured in earlier Suzaku observations, but
the surface brightness of the hot component is significantly lower than those
of the other regions. This means that these two plasma components are
physically separated and have different origins. The elemental abundances of O,
Ne and Mg with respect to Fe favor that the diffuse plasma originates from
core-collapsed supernovae or massive stellar winds.
