It's complicated because Japan, then and now:

1) is a place where symbolic and actual authority are two very different things.

2) is a place where outward consensus is prioritized. Heavily.

After the fall of Tojo in the middle of 1944, the cabinet which regained a modest degree of civilian control was split between those who wanted to surrender with one condition (the kokutai gets preserved in some form-this is what Truman eventually agreed to) and those who wanted to surrender, but with several conditions-they handle their own war crimes trials, all kinds of unrealistic stuff.

The thing is: the Soviet invasion of Manchuria, the atomic bombings, the potential social unrest, it all happened within the space of a week. It's frankly a bit bizarre to suggest that one and only one of these played a role in the Japanese decision to surrender, especially given the structure of their government. It probably all combined together at once. And even this led to the Kyujo incident.

>The Japanese military IN COLD BLOOD slaughtered more civilians than the Allies did in all their strategic bombings, let alone just nuclear. Even the nuclear bombs had military targets in mind...

Operation Meetinghouse killed more than the atomic bombs did. And the Soviets-quite literally-raped, murdered, and looted their way through Manchuria to the point where anti-Soviet demonstrations in multiple Chinese cities became very difficult for the KMT regime to control. The Americans would pardon Shiro Ishii, the Soviets would put several Unit 731 goons to work on their own human experimentation program at Sverdlovsk. And these were the relative good guys. So, yeah: it was a dark time in human history.

Ultimately, the decision to use the atomic bombs can't be separated from the decision to press for unconditional surrender of some kind. You could genuinely make the argument that Roosevelt was careless in applying something meant for Germany and its history to a completely different country with different pathologies, and it is certainly true that a "placated" Stalin, a strong pro-US nationalist China, a demilitarized irrelevant Japan, and a decolonized Asia were four goals that were never going to be compatible. But it didn't really matter for Truman, one of the few American Presidents who knew what war actually was-WWI as well as being descended from the losers in the Civil War-and someone who barely had the legitimacy needed to agree to keeping the kokutai after the atomic bombings. I think their usage was inevitable by 1945. Those incandescent with rage from 80 years later miss the forest for the trees.