Isn't that premise just Masayoni Son with his Softbank/Vision Fund
There's limits to how much an individual investor can make with their genius foresight (or literal foresight in the case of this LN I guess) due to the limits of the market when you become a truly big player.
Why not just have her reincarnate and become the PM or something if she actually wants to save the Japanese economy in this fantasy. Which would still be structurally impossible as America will force onerous terms on you, and one woman cannot force fundamental restructuring of the country even if they have power.
Maybe I'm just a bad fantasy writer and taking the premise too seriously.
Why are Germany and Japan on the dish Blinken? Why are you eating other diners at the table Blinken??