Harry Leferts
Suave Shadow Cabal Kaiju
Uh, just to point out that is a myth, there was no declaration of war until the next morning. What the Japanese did do just before the attack was send a message that they were breaking off negotiations with the Americans and that was it. And the plan for Pearl Harbor was all Yamamoto as the IJN needed a "Win" against the IJA politically hence why they tried to perform the biggest blow that they could, though he did understand that US was going to be a tough fight. As an aside though, the Japanese shipgirls could point out that the war was inevitable on the side of the Americans due to them doing everything possible to kick one off without firing the first shot. See the embargoes that the US put Japan under during the late 1930s and how during negotiations, they stated that there would be no serious ones until Japan left mainland China entirely. Not pull back to where they were before they kicked off the current fighting, but outright stating that they needed to pull back to the Japanese islands and Korea entirely before they would even start negotiating an end to the embargoes.(Frankly, I find it absurd the notion that a declaration of war delivered 30 minutes before an obviously intended surprise attack rather than two hours later is anything more than an imaginary line between honorable and dishonorable but Yamamoto believed in it and girls like Nagato and proud Kaga tend to be seen as sharing it.)
It could also go back a bit further if you wanted in some ways such as how the US used the WNT as a way to break England and Japan apart, up to actually spying on the Japanese diplomats to determine how far they could push it. As well to the Russo-Japanese War and its aftermath. Long story short, due to the war Japan was nearly broke and had a lot of young men killed and were looking for reparations from Russia for the war. And by normal methods, they should have gotten such for it. But the US was the Neutral Party in charge of deciding what would happen and, because now Japan looked like a possible rival, declared that Russia did not need to give up any funds and such. You can imagine how well that went down in Japan...