I live in Chiba near Tokyo. I usually go to shows in Tokyo. The venues are small but when some popular are bands doing shows, the venues are always full of hardcore kids.
We get some information about shows from band's websites or flyers that band members have distributed.
I think doing a band is quite tough in Japan. Almost all members of hardcore bands have another job like a salesman or a part-time job.
In my opinion, this is one of the reasons why they can't tour like famous bands from overseas.
Some Japanese bands are doing shows as support acts for overseas bands.
And some American bands have released split CDs with some Japanese bands like these...
WInds Of Plague/xAFBx/Loyal To The Grave
Sinking Ships/My Love/As We Let Go
There are so many great Japanese hardcore bands:
As We Let Go (Tokyo)
Ill Communication (ex-My Love) (Tokyo)
Nervous Light Of Sunday (Tokyo)
Silence Kills The Revolution (Tokyo)
Loyal To The Grave (Tokyo)
Crystal Lake (Tokyo)
Doggy Hoods (Tokyo)
Falling Apart (RIP) (Tokyo)
Anticipation (RIP) (Sendai)
No Choice In This Matter (RIP) (Tokyo)
Naiad (RIP) (Kyoto)
Keep Your Hearts (RIP) (Tokyo)
State Craft (RIP) (Tokyo)
Versus The Night (RIP) (Tokyo)
Hardcore more than music... You're right!