Hi there! I don't want to discourage any other answers that anybody might have, but I believe these older answers form the FAQ might help you out.

Would the Japanese have likely agreed to total unconditional surrender after just a "warning shot" pf the atomic bomb?

Why did Japan surrender?

There has been some controversy on the true effect of the atomic bombing of Japan. Was it the bomb, or the Soviet declaration of war that ended WWII?

What happened to the Japanese political/military landscape between August 6th, 1945 (the day that Little Boy was dropped on Hiroshima) and August 15th, 1945 (the day they surrendered). How did they come to the decision that surrender was the best option, and was there much disagreement?

Are Tsuyoshi Hasegawa's conclusions about the Soviet's influence in triggering the Japanese surrender of WWII widely accepted or are they in dispute? If he got it wrong, how did he get it wrong?

The really remarkable thing is that they did not surrender sooner, particularly when it became evident that Germany could not possibly win the war in Europe. Japan knew before they got into the war that they were no match for the United States in the long term. (Japanese navy admirals are on record as saying before Pearl Harbor that they could hope, with a sufficiently good result there, to be able to handle the US Navy for six months. Apparently they were aware that the US had shipyards on the mainland and enough industrial capability to supply them.) To have any hope of a favorable outcome, Japan was absolutely reliant on Germany to win in Europe and come to Japan's assistance in the Pacific theater.

In order to understand why Japan did not make peace sooner, when they could have negotiated a less disruptive result (the US was tired of war and would have given much to get out of it; Japan probably could have kept Korea, for example, if they'd negotiated it around the time of VE Day, and they certainly could have kept Etorofu if they'd surrendered any time before Russia occupied it), you have to understand the internal power structure in the Japanese Empire at the time, as well as certain aspects of Oriental culture (e.g., the emphasis on fatalism).

However, this doesn't answer your question. It just reframes it: "What finally changed after Nagasaki?"