Hello, I was playing around with my savedata for Monster Monpiece (JP) (PCSG00148).
Not sure if this will be useful for anyone. Seems to be the same as the US and EU offsets.
Monster Monpiece (JP):
//Found in SystemData_0000.sav
Money 0x1A724
Rub Points 0x1A728
Red Key 0x1A72C
Blue...