  We observed near-Sun comet 323P/SOHO for the first time using ground and
space telescopes. In late December 2020, the object was recovered at Subaru
showing no cometary features on its way to perihelion. However, in our
postperihelion observations it developed a long narrow tail mimicking a
disintegrated comet. The ejecta, comprised of at least mm-sized dust with
power-law size distribution index $3.2 \pm 0.2$, was impulsively produced
shortly after the perihelion passage, during which $\gtrsim$0.1-10% of the
nucleus mass was shed due to excessive thermal stress and rotational
disruption. Two fragments of $\sim$20 m in radius (assuming a geometric albedo
of 0.15) were seen in HST observations from early March 2021. The nucleus, with
an effective radius of $86 \pm 3$ m (the same albedo assumed) and an aspect
ratio of $\sim$0.7, has a rotation period of 0.522 hr, which is the shortest
for known comets in the solar system and implies cohesive strength
$\gtrsim$10-100 Pa in the interior. The colour of the object was freakish, and
how it changed temporally has never been previously observed. Using our
astrometry, we found a strong nongravitational effect following a heliocentric
dependency of $r_{\rm H}^{-8.5}$ in the transverse motion of the object. Our
N-body integration reveals that 323P has a likelihood of 99.7% to collide with
the Sun in the next two millennia driven by the $\nu_6$ secular resonance.
