If your opponet goes 100% kill Japan first, then there is nothing you can do as Japan. The game for the axis will then be won as Germany. Japan needs to do 2 things.
One is buy a ton of navy. Japans first turn is the most important for her. UK killed your BB/Carrier off indonesia then you will be needing to buy sea units. You will have 2 transports, and I’d advise to build only sea/air units the first turn with Japan. Mainly air since US can aways see this and just not go after Japan, and then you are stuck with a bunch of worthless subs or destroyers. Every turn after the first turn if US is putting 100% of her money into Navy, then Japan needs to invest all of her money minus 2-4 infantry or so into navy as well. The longer you can stall the US from taking one of the islands and building an IC there, the better.
The scond thing Japan needs to do is to take as much territory as she can. Take all of russia’s northern territory, and have a couple units that can trade kazachstan back and forth with russia, while the majority of your forces should be in the south keeping UK India at bay. You won’t ever be able to take out UK India if the allies do a true KJF strat and UK plays it correctly, without compromising the pacific to US’s navy too soon. Say you have 4 transports. 3 of these taking units from japan to the mainland, and 1 picking up units from your islands then that meant you spent 14 into transports and 6-12 more IPC’s into ground untis a turn. US should have way more sea units than you and just walk all over the pacific. You also have to remember that UK is buying 2 fighters a turn, and by UK turn 4 should have 6-8 fighters and a bomber that are UK controlled that can hit your ships if they are off french indo china.
Japan should be up 8 IPC’s by the end of their second turn, and making as much as the US. By turn 3 they can be up even more and now they are out producing the US
you don’t like the complex on mainland idea?