The (in)validity of a system coupling the cubic, nonlinear Schrödinger equation (NLS) and the Korteweg-de Vries equation (KdV) commonly known as the NLS-KdV system for studying the interaction of long and short waves in dispersive media was discussed in part I of this work [N.V. Nguyen and C. Liu, Water Waves, 2:327–359, 2020]. It was shown that the NLS-KdV system can never be obtained from the full Euler equations formulated in the study of water waves, nor even the linear Schrödinger-Korteweg de Vries system where the two equations in the ...