@hedgemoney for the sake of discussion, japan have to change from the democratic free government to authorial like ww2 government to survive, at least till thing turns normal
Fuel and electricy will be hard to solve but there's restriction like to only have only electric/hybrid on electric mode cars on the road this might only cover 1% of cars in Japan but there's factories that probably have them in storage for foreign trade that they can use in the country. Transport will be Cuba like level where everyone can hitch a ride if the person is driving there. But fortunately public transport is good in Japan and people can use horses or bikes if they want. The rest that they save up will be used for trucks across remote inland Japan for food or the people living there will be temporary moved to the city to save fuel reserve, I would argue the the highnspeed trains can be used for transport of goods but normal trains is good, they might need to use steam locomotive s from their museums lol, And the remaining saved fuel needs to be given to the army and transport for building the oil well. Maybe excess food from the ally country can be used for making bio diesel (though need a specialized diesel engine to use it)
the army can't use mobile units as much as they want and I think it will be a good idea of the government to use the lousian empire as a buffer zone, while showing their might and intent. This might buy them some time to begin producing oil.
On the construction of railway and oil wells well there's not a lot to learn the people living on the continent how to build a decent railway, hell Chinese peasants built American ones fast in the1800s, with magic users that can lift and do majority of the work. Also it don't have to be that the railroad need to be first build! Having to transport oil drilling equipment by vehicle to build it up first is probably their number one priority if the roads are suitable it will be more easier to have a convoy transport equipment on the site and build the wells, if not they have to find a flat land to land the cargo plane or use cargo helis. For them to get more oil than they use on the convoy trip is more important so they can start small and grow big. Also the railway can be a side project while they are building the well. Work culture is insane in Japan and all those who works with oil have to take double shift so I suspect they can make a well and produce oil in 2 week instead of the 1-3 month period
Electricy is different, one way is to limit what they can be used for, like only household and essential buildings and some factory for domestic productions or military. Night light will be different because they need to conserve energy. There's still a lot of nuclear plants in japan and they produce about 30% of electricity, nuclear might last them at least till oil is in reach. There's still the problem with coal power plant which Japan relies at least 30% on, there's probably enough coal in the ally continent to supply 1 or 2 coal power plant reliably, on the other hand Japan has a lot of power dams which produce about 1/3 of coal, some more than coal.
Food can be solved with strict rationing if they need more time building the oil infrastructure! they will have to survive on famine food, resulting in eating their pets or whatever moves. Tho we are not sure how much fishes there are in the ocean, given its far from the continent there might be a lot there. japan will not need the overfishing restriction that they have now since it's a newly ocean. So in general they have to survive on fish, rice and whatever they can find til the continent transport enough food.
As for social it will be a mess, imagine you have To to live like a commie to survive. The non essential will have to be forced to work as fishermen or farmers, railway worker, ammo factory worker andthe rest could probably teach the new people's modern technology. Crime would surely ride for a bit. Japan have to put reserve as "policemen". But seeing how most country react in the time of crisis even in covid 19, this might not be so dark after all. Also Japanese are seen as a polite and understanding people. If a chunk
could emmigrate to the continent there would be less to worry for them and I believe they would have a easy time adapting or start a life there.
You have to remember it's pure entertainment and there's magic and shiiiet. But I do think they can survive a month before chaos as commies, which should be enough to get their oil production running to return to normal