Not duplication) I couldn't find the answer for the general case, instead of the special case that I already seen in Youtube I hyperlinked.
I will fully satisfy with not only a mathematically rigorous proof, but also just any argument.
For example, I was impressed by the thought experiment(in Youtube : https://youtu.be/hW7DW9NIO9M ) arguing the equivalence principle for the special case that the rest mass of an object actually turned out to be a part of total energy of the object.
Is there any argument like that, but for the general case that the total energy(= rest E's + kinetic E's + potential E) of a system must be the total mass of the system which determines the amount of gravitational attraction and resistance for an acceleration? I think it might require the general relativitistic consideration.