Here is the link to the story.
Commenting on the bombs is highly unusual in Japan, on one side because of the obvious pain still there by survivors and their families, but also because of the close ties between Japan and US.
The speech of the minister itself got flooded under angry comments about the number of casualties and sufferin, so he apologized for it, but for me the most important line in his speech is this:
The US, he said, must have thought the bombs "could prompt Japan's surrender, thus preventing the Soviet Union from declaring war against Japan".
There are many historians that believe this actually was the one and only reason the USA dropped the bombs on Japan... And there are many arguments that speak in favour of this idea.
The idea is that the Soviets took the opportunity to expand their sphere of influence. The USA was shocked to see that the Red Army took control over Eastern Europe (even in nations that before were under "Western" influence), and that it even reached Berlin. But of course that could not be said, since they were allies (the Yalta agreement). Stalin had told the USA that he would first deal with Europe, and then afterwards "assist" the USA in the Pacific War.
Many believe that the thought of the Soviet Union taking some Asian countries and thus expanding it's influence, or even more horrific, the idea of the Soviets invading Japan, and dividing it like Germany (an East and a West Japan, so to speak), was simply unacceptable to the USA. So they decided to end the war as fast as they could (before the Soviet army could move into the Pacific), and use the atomic weapon.
Some other arguments: Japan had already offered to negotiate a form of surrender with the USA in the days before the bombs were dropped, so the USA knew surrender was something that was only a few weeks/months away at worst. Secondly, Japan is an island, and the Japanese army was beaten in the Pacific, only Japan itself was left: a simple lockdown of the island, and any island runs out of resources (the exact reason Japan started the war in the first place: no resources).
I'm afraid this is something that will remain in the dark forever, but it's actually the first time I hear a high ranked official of any of the countries involved talk about this theory... Until today I had only read it in historical papers.