Every time I hear of utilizing the Moon for anything, I generally assume that highest degree of reasonable applicablity is Helium-3 extraction. Fortunately for people interested in this topic, the media tends to find it fairly interesting:
Given the current state of affairs on Earth, energy policy is becoming increasingly important and open to innovative and non-conventional solutions. He-3 fusion is certainly an excellent medium- to long-term alternative to
<environmentalist> completely and irreparably destroying the environment for no reason by ignoring obvious externalities
</environmentalist>. Japan has traditionally been fairly open to the nuclear option and, recent difficulties aside, will probably continue to look toward nuclear in the future. Fusion is substantial more desirable than fission, of course, and many would argue that He-3 will trivialize some subset of the problems facing fusion development.
In terms of how, we aren't really actually sure how much He-3 there is, how to extract it, how to return it (or even if the reactors should be on lunar surface or in orbit and energy otherwise returned). And of course, there's always the possibility that there is other, unexpected mineral or otherwise wealth to be harvested. I'd expect some InSight like drilling operation with a goal of sample return rather seismic modeling. At least, if I were JAXA, that's what I'd do.