XRISM is an international joint satellite mission by Japan, the United States, and European nations aimed at high-resolution spectroscopy of high-temperature plasma in the universe. Professor Shunji Kitamoto, Associate Professor Shinya Yamada, Assistant Professor Makoto Sawada, and graduate students at College of Science, Department of Physics have been members of an international team formed by Japan (JAXA, Tokyo Metropolitan University, Rikkyo University, etc.), the United States (NASA, LLNL, etc.), and the Netherlands (SRON) to jointly develop Resolve, the soft X-ray spectrometer onboard XRISM. Resolve uses a microcalorimeter detector array cooled to an ultra-low temperature of only 0.05 degrees above the absolute zero to precisely measure energies of X-ray photons from high-temperature plasma. The spectrometer enables precise and accurate determination of the temperature and elemental composition of plasma. Furthermore, it enables measurement of bulk and random plasma motions, which have previously been difficult even to detect. After about three months of the commissioning period for the spacecraft and payload instruments, the XRISM satellite will start scientific observations.