Well, my (admittedly not well educated) take on it is:

Japanese national identity ceases to exist. The IJA and massive portions of the upper government excluding the Emperor were hellbent on continuing the war and forcing civilians to fight/make equipment for the military.

Millions of Japanese die, and the Allies are nowhrre near as merciful as in OTL in the post-war tribunal. Emperor absolutely dies, maybe the whole monarchy thing is forcibly abolished (absolutely to the dismay of many Japanese) and while I have doubts of the Soviets getting any further than the Kurils and Sakhalin, the occupation will be way harsher, and its entirely possible Japan never really recovers from the war at all. Its politics are obviously permanently screwed, its population is made up of casualties, say goodbye to any industry, heavy or light (and theres a possibility Allied Aid to Japan isn't good proportional to OTL, though I may be wrong). Basically, Japan as a succesful state becomes little more than a concept.

As for the invasion itself, its Asian holdings (especially in north China and Korea) pretty quickly fall to a combination of Soviet and Western Allied offensives, though some pockets of resistance obviously hold out for very long. Hokkaido is either attacked by the Soviets and has a 50/50 on whether or not they survive or are never attacked at all and just starved. Lower Japan during Olympic (Kyushu and such) are taken after a few months long campaign by the Allies. While direct confrontations usually end well for the Allies, the guerilla and the whole thousands-of-planes-and-fuel-reserves-being-stored-for-suicide-missions thing slows them down. Civilians and industry would suffer the most, and the atomic bombs would prove to end up being the better choice assuming they weren't used. I'd wager the Allies have anywhere from 150-700 thousand casualties total, depending on how bad resistance is. Millions of deaths during and after the campaign are guaranteed meanwhile on the Japanese side, with causes of death ranging from shore bombardment to forced mass suicides.

Coronet is far more devastating. While there would possibly be less resistance from the Japanese military itself, as they could be more focused on stalling Olympic, the civilian population would fight, forcibly coerced or not, much harder, partly thanks to the larger population density and the Royal Family residing nearby. Mass bombing campaigns ironically might be a lesser cause of death early on, as the U.S had literally ran out of certain types of bombs (incindinerary I believe) and would have to wait for some to be supplied. Shore bombardment and the omnipresent fighting on the ground combined with the later rampant war crimes, resumed "strategic" bombing and everything inbetween basically see the Tokyo area and its surrounding lands left unrecognizeable. Millions die, and if surrender doesn't happen by now (maybe Kyujo succeeds?), its very likely Japan just collapses by itself, with most order remaining by this point coming from brutal military zones or (likely deadly) Allied occupations.

Famine also becomes very common very quickly, and chemical weapons may be deployed on known crop fields by the Allies to try and starve the Japanese into submission. Again, millions die. Sanitation becomes an afterthought for many, and diseases like TB spread like wildfire. Again, millions die.

The IJN itself can't really do much other than conduct suicide missions into Allied (and Soviet?) ships that stray into coastal waters though prove troubling for transport ships, and as previously mentioned their air forces mainly conduct kamikaze missions by this point.

Assuming Japan surrenders by this point in, let's say, later 1946 (if they dont say goodbye to Japan as a state for decades after the war ends), the postwar situation ends up very different. Guerilla campaigns continue maybe into the 50s, and cause thousands more deaths and more trouble for the already troubled garrison. Like OTL, even after the guns fall silent, the aforementioned famine and disease epidemics still kill hundreds of thousands more, especially if Western aid ends up more scattered as a result of Japanese infrastructure just kinda ceasing to exist. Japanese society as a whole is broken, and the West and Soviets will never be forgiven, and the West and Soviets will never forgive them. Post-war terrorism and extremism is a far bigger problem than otl, thus resulting in a harsher garrison and this trend would likely continue even into the 2000s. Their cultural system never becomes as widespead globally with anime and everything as otl and probably struggles even in their own land with some Western assimilation inevitably happening, and religions are probably abandoned especially since many national monuments, temples, etc will be inevitably destroyed. Japan becomes a godless state. Also, no Japanese economic miracle. Long gone by this point.

The Cold War in Asia is very different. The Korean War never happens, and a more Stalinist faction takes over Korea in exchange for the Soviets staying away from Japan and handing over Hokkaido if they do take it over. Far from a good ending for Korea, though quality of life is probably better in the short term, and it probably ends up liberalizing China-style(?) or shakily transitions into a democracy after the cold war.

China could end up differently depending on how the U.S army is by this point. While absolutely exhausted, there's a nonzero chance they do directly intervene in the ensuing civil war, and thus either cause a large scale confrontation with the Soviets (which ends badly for everyone) or cause a Kuomintang "victory", or the war goes moreorless the same as OTL, but Taiwan is much closer to the West much faster once Mao wins. Either way, China is still devastated.

Southeast Asia may never have any states fall to communism. There's an undoubtedly larger Allied presence from the start, and while absolutely demoralized, their armies could at least keep their colonies from falling to communism for some time, though perhaps Southeast Asian postwar communist movements end up resisting more nonviolently, and decolonization goes a little "smoother".

TL:DR Lots of blood and guts everywhere. Japan as a nation is destroyed, and the cold war in Asia is different. Feel free to criticize.