Little did Nirval realise that by diverting the miasma to Earth, she would only grant Earth a free supply of energy that can be harnessed through the power of science. However, energy can't be created out of nothing, so in fact the gate would leech energy away from Nirval's own world, making it weaker. Most likely it would be the energy used for magic. If too much of it is spent, magic would disappear from that world. You can bet Japan would spend as much of it as possible, to make electricity as cheap as possible for the Japanese industry and citizens.
I don't think Nirval would be celebrated as a hero for too long.