The Focusing On Relativistic universe and Cosmic Evolution (FORCE) mission is proposed as a future Japan-lead X-ray observatory to be launched in the mid 2020s. FORCE is a successor of Hitomi, focusing on the braodband X-ray imaging spectroscopy in 1--80~keV with a significantly higher angular resolution of $< 15''$ in half-power diameter. The sensitivity above 10 keV will be 10 times higher than that of any previous hard X-ray missions with simultaneous soft X-ray coverage. The satellite is planned to be launched by the Epsilon vehicle by ISAS/JAXA. In the current design concept, FORCE is equipped with three identical pairs of supermirrors and wide-band X-ray detectors. The focal length of the mirrors is 10~m. The silicon mirror with multi-layer coating is our primary choice of optics to achieve a good angular resolution for the wide energy band while maintaining a light weight. The detector is a hybrid of a SOI-CMOS silicon-pixel detector and a CdTe detector responsible for the softer and harder energy bands, respectively. It is basically a descendant of the hard X-ray imager onboard Hitomi with its soft-band detector replaced with the SOI-CMOS. The primary scientific objective of the FORCE mission is to trace the cosmic formation history by searching for ``missing black holes'' in the entire range of the mass spectrum of BHs: ``buried'' supermassive black holes (SMBHs) ($>10^4~M_{\odot}$), intermediate-mass black holes ($10^2$--$10^4~M_{\odot}$), and ``orphan'' stellar-mass black holes ($<10^2~M_{\odot}$). Also, investigation of the nature of relativistic particles at various astrophysical shocks is in our scope, with high-angular-resolution X-ray observations with the broadband coverage. FORCE will open a new era in these fields.