What I was suggesting was that the Japanese time traveler would be... removing obstacles from the path of what will be the US Juggernaut in an attempt to save more lives in the long run. I sort of have a handle on the Japanese military mindset from that time on their inability to contemplate surrender.
What I'm arguing is in the same vein of the idea that the US using nukes led to less death in the long run. I'll explain more if someone wants to continue this line of thought.
That's possible, but it's probably unworkable. For one, working to sabotage their own country would be a
really good way to run afoul of their subordinates and superiors since that is treason at a time of war. At this point in time, the IJN (and IJA) were pretty factionalized and there was also a rather nasty secret police in the
kempetai, who were specifically charged with insuring loyalty to the war effort by Prime Minister Tojo. It's the same problem Admiral Schreiber has, the secret police
is watching for disloyalty and would love to take a rival service down a peg with a treason case. Sure, it's theoretically workable, but realistically it has enormous potential to backfire horribly for our hypothetical time traveler.
Another problem is that in order for the surrender to 'stick', the party in question has to feel psychologically defeated. In OTL, it was clear that Japan had lost the war and the militarists were discredited. Compare that to World War I, where Germany was
not fighting on it's own soil and it could be and was argued that Germany was winning until the 'stab in the back'. While our hypothetical time-traveler could take some steps to prevent certain atrocities (such as arranging the destruction of Unit 731), realistically at this point, the only question for Japan is how long it takes and how bad the beating they will take will be.
EDIT-One further issue. How does our IJN admiral convince his kanmasu?
Saratoga and the rest are trying to minimize the damage from a military defeat along the path to victory in the pacific.
Bismarck and
Blucher are in a service that already lost to the Royal Navy once before, are grossly outnumbered by the RN now, and he can specifically point to their sinking as a byproduct of challenging the preeminent naval power.
In the IJN, it's quite different. They have a legacy of victory in WWI, Tsushima and so on versus the German navy's legacy of defeat. Likewise, they view themselves as a peer competitor to the USN/RN in the pacific, which at this point is not totally inaccurate since while the other two services are larger, they also have more ocean to cover. Finally it's highly likely that the hyper-militarism of the last decade has shaped the kanmasu, so you will have a lot more attitudes like
Kaga than anything else.