  FORCE is a 1.2 tonnes small mission dedicated for wide-band fine-imaging
x-ray observation. It covers from 1 to 80 keV with a good angular resolution of
$15"$ half-power-diameter. It is proposed to be launched around mid-2020s and
designed to reach a limiting sensitivity as good as $F_X (10-40~{\rm keV}) = 3
\times 10^{-15}$~erg cm$^{-2}$ s$^{-1}$ keV$^{-1}$ within 1~Ms. This number is
one order of magnitude better than current best one. With its high-sensitivity
wide-band coverage, FORCE will probe the new science field of "missing BHs",
searching for families of black holes of which populations and evolutions are
not well known. Other point-source and diffuse-source sciences are also
considered. FORCE will also provide the "hard x-ray coverage" to forthcoming
large soft x-ray observatories.
