Extremely metal-poor (EMP) stars are the living fossils that hold records of nucleosynthesis in the early Universe. Their small metal contents indicate that EMP stars formed in clouds enriched by supernovae (SNe) of the first-generation of (Pop III) stars. First, we investigate the metal enrichment process from Pop III SNe with cosmological simulations. In a dark matter halo with a mass of ~ 10<sup>6</sup> M<sub>sun</sub>, a Pop III star with a mass of 13 M<sub>sun</sub> forms. After it explodes as a normal core-collapse SN (CCSN), metals are dispersed into the intergalactic medium. A fraction of metals can return to the halo that have hosted the Pop III star, and the enriched gas collapses again. We find that the iron abundance of the cloud center is [Fe/H] = -3.6, consistent with observed values of EMP stars. We further study the formation of carbon-enhanced metal-poor (CEMP) stars, which have larger carbon fractions than the solar ([C/Fe] > 0.7). Employing a faint CCSN model, we find that the carbon abundances in enriched clouds are A(C) = 3.8-5.1, smaller than observed values. <br>
Next, we follow the star formation process in enriched clouds with metallicities 0-10<sup>-3</sup> Z<sub>sun</sub>. With a cell refinement technique, the spatial resolution can reach ~ 0.01 AU. As a result, the clouds contract gravitationally, and hydrostatic cores (first cores) form in the central, optically thick regions. We hereafter call the first cores as protostars for simplicity. The protostars accrete the gas with finite angular momenta, and accretion discs form around the protostars. We find that the discs fragment into multiple secondary protostars because the discs are gravitationally unstable due to radiative cooling from dust grains. At most 26 protostars temporarily form in each disc, but most of them merge with each other. Finally, 1-3 protostars survive, forming hierarchical binary systems.