Japan has a lot of stag beetles..Prosopocoilus? Dorcus?
Prosopocoilus has a chance if you squeeze your substrate tightly. I personally don't know any Japanese Dorcus that doesn't need a log to breed.
As for Phalacrognathus muelleri, I have always used a log to breed. However, the trick for this species is to use substrate that is grinded very finely (very tiny particles). Give it a try, maybe you don't need a log at all!