The paper ‘Measuring the asymmetric expansion of the Fe ejecta of Cassiopeia A with XRISM/Resolve’, by Dr. Bamba, has been accepted for publication in the special XRISM issue of the journal PASJ. In this paper, we observed the supernova remnant Cassiopeia A (Cas A), which is about 350 years old, with XRISM, which has excellent energy resolution, We showed that the plasma containing iron elements shows red-shift in the north-east and blue-shift in the south-west. From these observational facts we have identified that in Cas A fragments of the pre-explosion star are scattered in non-isotropic directions. These results are consistent with Neutrino-driven SN scenario, and are important not only for showing how heavy elements are scattered into space, but also for providing insights into the supernova explosion mechanism. For more information. For more detail, please check arxiv.