I've kinda gone away from screamo in recent times. Just like most sub-genres most of the bands therein sound really similar to each other. Or at least too similar for my tastes. But there's a whole bunch of bands that seem like they'd be really great that I just haven't gotten around to listening to yet.
Yolz in the sky, Tiala, Kulara, there is a light that never goes out/Z, envy, and killie would probably get my vote as the best "screamo" in japan. I guess Melt-banana and rin toshite shigure probably qualify as screamo too. They certainly scream anyway.