An important path to improving the supercapacitor energy density is to aid superior electrode capacitance materials by designing a binder-less electrode with porous and hierarchical nanostructures for maximum utilization. In this work, we illustrated that the copper manganese sulfide (CuMnS) nanostructures were decorated on Ni foam (by a hydrothermal process) as a positive electrode of the asymmetric supercapacitor (ASC) for the first time. The physiochemical characterization, such as XRD, FE-SEM, HR-TEM, Raman, and XPS analysis, confirmed the formation of the CuMnS nanostructures. The cyclic voltammetry study using three-electrode measurement shows the occurrence of battery-like charge storage (Type-C) property of the CuMnS/Ni electrode. The CuMnS/Ni electrode delivered a high capacitance of 1096.5 F g−1 (182.75 mAh g−1) as measured from the charge-discharge analysis at a current density of 2.5 mA cm−2. In addition, the device performance of the CuMnS/Ni electrode was examined by constructing the asymmetric supercapacitor (ASC) using two different electrodes (CuMnS/Ni as a positive and graphene as a negative electrode). The constructed CuMnS//graphene ASC shows a high device capacitance of 217.37 F g−1 with ultra-high energy/power densities of 77.28 Wh kg−1/36,363.63 W kg−1 with remarkable cyclic life. These overall performance merits of the CuMnS//graphene ASC can be used as potential alternatives for the future generation of high-power/energy-density supercapacitors.