  Starless dense cores eventually collapse dynamically, which forms protostars
inside them, and the physical properties of the cores determine the nature of
the forming protostars. We report ALMA observations of dust continuum emission
and molecular rotational lines toward MC27 or L1521F, which is considered to be
very close to the first protostellar core phase. We found a few starless
high-density cores, one of which has a very high density of ~10^7 cm^-3, within
a region of several hundred AU around a very low-luminosity protostar detected
by Spitzer. A very compact bipolar outflow with a dynamical timescale of a few
hundred years was found toward the protostar. The molecular line observation
shows several cores with an arc-like structure, possibly due to the dynamical
gas interaction. These complex structures revealed in the present observations
suggest that the initial condition of star formation is highly dynamical in
nature, which is considered to be a key factor in understanding fundamental
issues of star formation such as the formation of multiple stars and the origin
of the initial mass function of stars.
