I agree with Guitarmanlp, Japanese porn makers should take care to preserve their unique and excellent style - it's mostly all we watch, Euro and Japanese.
From watching hundreds of Japanese sex films we're left with the impression that most Japanese men are sexual cripples, either pathetic quivering little boys or brutish bullies, maybe 20% sexually informed as giving and caring about their sex partner. Perfectly natural Japanese women enjoy bisexual relations just to get some deeper sexual satisfaction.