Trying to have Japan deplete their resources is surprisingly a sound strategy from them, not that it will work because they don’t have enough to stop them. Japan cannot replenish their weapon at the speed they’re being used. When it comes to advanced weapons they require imports which they do not have here.
You'd be surprised how many military vehicles and weapons Mitsubishi, Kawasaki, Toshiba, Matsushita, Nissan, etc make, not just kei cars, motorbikes and electronics. 90% of Japanese military material is made locally from their own original design or licensed, in very rare instances they have directly imported like recently the F-35, V-22 and Tomahawks where licenses for local production are not granted.
I already wrote a pretty long explanation a few chapters back for someone who though that 90% of the JSDF weapons have been provided by the USA and 10% locally when it's the other way around, 90% of their military equipment is made locally and the rest is directly imported. Not gonna repeat myself. It's just stupid to think that even for basic stuff like a Snakeye or dumb bomb (which BTW the ones dropped in this chapter by the BP-3's are just plain Mk. 82, not Snakeyes FYI) they'd depend on the USA, when they have more than capable local manufacturing and done so. Which BTW should I say that the standard Mk. 82 bomb is not just exclusively made in the USA, Rheinmetall in Germany, Safran in France, Nitro-chem in Poland makes the too and countless other military manufacturers in various NATO countries too as well as Japan. What's next? That they'd need to purchase all their 5.56mm and 7.62mm ammunition for their Howa Type 89, 64 and 16 rifles from the USA because it's a Murrican ammunition? It's not like being transported their military manufacturers would forget how to forge munitions and the chemistry of explosives.
I'd recommend you better inform yourself how much of their military is manufactured locally. Yes they have depended on the USA for some of their designs and licenses for the manufacture which include the blueprints, tooling and jigs provided, but besides that all materials, manufacture and labor are done by the japanese themselves. They have a very long history of producing military hardware under license in Japan. Not to mention that being separated from Earth, it's not like they'd have to give accounting or royalties back to Lockheed Martin, Boeing, GE, P&W, etc if they just suddenly increase production of licensed hardware like suddenly Mitsubishi made a few more F-15 and F-2 in their factories from the ones they've already done for the JASDF. Or Fuji Heavy Industries finish manufacturing the rest of the 50 or so AH-64 they paid the license to Boeing to produce locally or make a few more AH-1s for the JGSDF. Or IHI having to tell General Electric or Pratt & Whitney how many more GE F110 or P&W F100 engines they suddenly made as spares for their military planes.
I wonder if this foreshadowing, as logistics would absolutely become the bane of the JDF in this situation. They simply do not have the facilities to replace those missiles, and eventually even the spare parts for their jets are going to run out. Other countries (US, China... France to some extend, Russia because of old USSR stocks) would have fared better. Ironically this makes the JDF being a much more interesting protagonist in the story...
Almost all their homegrown missiles and foreign licensed missiles of all kind & varieties are made by Mitsubishi Heavy Industries, they do have the facilities to manufacture more advanced weaponry than you'd think. It's just a matter of budget and raw resources, which by the way have been hand waved with their diplomatic relations with the countries Parpaldia have tried to invade or strong arm.