I bet Japan's going to be internally forced to expand rice exports, not imports. Farmers must pay bills or else they go away, and people aren't going to eat imports. So farmers has to stay by either completely subsidized a la defense production, or by scaling out at paces permanently exceeding inflation. Maybe both. Extra production has to go somewhere but population is on decline, so it has to go somewhere beyond the seas.
Unless iPhone moment happens and the country's hit by vastly superior rice, which iOS was - iPhone had worse hardware with worse integration than any of local phones back then, but UI/UX was literally 5-10 years ahead of everything else, and it completely replaced the entire Japanese phone market helped by blatantly illegal marketing tactics. That's not happening so far with rice.