  We present the results of near-infrared (NIR) multi-epoch observations of the
optical transient in the nearby galaxy NGC300 (NGC300-OT) at 398 and 582 days
after the discovery with the Infrared Camera (IRC) onboard AKARI. NIR spectra
(2--5 um) of NGC300-OT were obtained for the first time. They show no prominent
emission nor absorption features, but are dominated by continuum thermal
emission from the dust around NGC300-OT. NIR images were taken in the 2.4, 3.2,
and 4.1 um bands. The spectral energy distributions (SED) of NGC300-OT indicate
the dust temperature of 810 (+-14) K at 398 days and 670 (+-12) K at 582 days.
We attribute the observed NIR emission to the thermal emission from dust grains
formed in the ejecta of NGC300-OT. The multi-epoch observations enable us to
estimate the dust optical depth as larger than about 12 at 398 days and larger
than about 6 at 582 days at 2.4 um, by assuming an isothermal dust cloud. The
observed NIR emission must be optically thick, unless the amount of dust grains
increases with time. Little extinction at visible wavelengths reported in
earlier observations suggests that the dust cloud around NGC300-OT should be
distributed inhomogeneously so as to not screen the radiation from the ejecta
gas and the central star. The present results suggest the dust grains are not
formed in spherically symmetric geometry, but rather in a torus, a bipolar
outflow, or clumpy cloudlets.
