TRUE GORE actually isn't Japanese, it was made by San Francisco Industrial, noise artist prankster Monte Cazzazza. But it only got a legit release in Japan so most people think it is Japanese. There was a sequel called EMPIRE OF THE SENSES.
As for the others if you've seen the abominable Todd Tjersland mondo series FACES OF GORE then you've seen these Japanese mondo/death tapes as 90% of the footage in the FOG series is lifted directly from them except with new, nauseating propaganda narration that is way more offensive than the footage itself.
I haven't see but one of those actual tapes (one of the DEATH FILES, don't recall which one) but they definitely had legit releases in Japan. There is a huge market for all things grotesque and death related over there. There's videos, books, magazines and lots of artists that all work in that dark part of the subculture.