Remove scales from sardines using the tip of a knife. Cut off the head at the base of the pectoral fin, and remove the guts by slicing the belly slightly. Rinse with water and pat dry with kitchen paper.

Mix the seasonings (water, sake, mirin, soy sauce) in the inner pot of the pressure cooker. Add sardines, pickled plums, and ginger slices. Set the pot into the cooker.