Maybe the Soviets invaded earlier?
They had little incentive to do so, and even less logistical capability.
First of all, they were apparently reasonably content to let America reduce Japan while they focused on putting themselves into a position to steal half of Europe. There's a lot of debate on whether Truman had to drag the Soviets into the Asian war or had to slow them down to keep them from barging in, but in either scenario it didn't give Stalin a significant strategic advantage to invade any earlier than he had to. Every day that we bled a little more out of Japan made it that much easier for him to walk in and plant a flag on Japanese soil in time to earn a seat at the table when it came to dividing up Japan. It wasn't as important for them to invade early as it was to simply invade before it was over.
Now. Having said that, yes - in a perfect world, if he could have just walked ashore in Hokkaido with 4 or 5 divisions and established a comfortable beachhead, then of course it would have been to his overall advantage. But it was never as easy as that, and trying to force the issue would have come at considerable cost.
Stalin had promised Truman at Yalta that he would declare war on Japan within 3 months of the surrender of Germany, and that date would have been August 8. As of July 15 or 16 (can't recall exactly), Marshal Vasilevsky (Commander in Chief of Soviet Forces in The Far East) cautioned Stalin that he was not yet ready to attack Manchuria (let alone invade the Home Islands). On August 3, he notified Stalin that Manchuria was a go any time from August 5 onward. It wasn't as though Vasilevsky was just sitting around surfing porn on the internet; Stalin had made it clear that being in a position to attack Japan as early as possible was a very high priority, and Vasilevsky was doing everything he could to make that logistically viable. It just was not possible to get all those pieces in place.
Stalin understood this, and apparently accepted it. Given everything he had to work with at the time, it appeared that the United States would probably not be on a position to invade Southern Japan any sooner than October or (most likely) early November. Given Stalin's strategic goals, invading Northern Japan anytime as late as September or early October would have given him a seat at the table when it was time to carve the turkey. So attacking the Kwangtun Army in Manchuria in early August was a perfectly reasonable and entirely acceptable step on the path toward his strategic objective, and in fact probably gave him much more breathing room than he thought he needed.
Could Russia have invaded Hokkaido before early August? Debatable, but arguably possible, I suppose. Would they have had a good reason to try it? Not by any standard that I would consider reasonable, unless they had made it a priority at least a year earlier, at a time when they needed every man, every gallon of gas, and every drop of blood to roll the German armies back to the west. I think it's a huge stretch to imagine the Red Army invading Japan before the bombs were dropped.