XRISM Resolve spectra synthesized from model B18.3 at an age of 500 years (corresponding to the year 2487). The upper panel displays the full spectrum in the [1.0, 10.0] keV energy range, while the four lower panels provide close-up views of selected emission lines: Si XIV (2.1 keV), SXV (2.46 keV), Ar XVII (3.14 keV), Fe XXV (6.7 keV). The top axis of each lower panel represents the corresponding Doppler shift velocities relative to the rest-frame wavelength of each line. The figure includes the ideal synthetic spectra (black lines) and the contributions from individual plasma components: shocked CSM (blue), shocked H envelope (green), and shocked pure ejecta (violet). The lower panels emphasize the contribution from shocked ejecta (H envelope + pure ejecta) using a shaded yellow region.