"I don't understand this phenomenon," he told the conference.
Hirose added that the vast utility was diversifying its energy sources in order to reduce costs.
But officials from gas-producing nations said Japan and other energy importers needed to shoulder some of the high costs of LNG production.
Mohammed Bin Saleh Al-Sada, minister of energy and industry in Qatar, said LNG required large investments and long-term consumer commitment. At an LNG producer-consumer conference in Tokyo, the world's largest importer of the fuel, industry minister Toshimitsu Motegi complained about a so-called "Asian premium".
"There is strong concern among the public over the surging demand and soaring prices for LNG," Motegi said in his keynote speech at an event bringing together more than 1,000 officials and business people from about 50 economies.
"Increases in fuel procurement costs impose a heavy burden on the Japanese economy," he added.
Japan and some of its fellow Asian neighbours hav