NSPIXP-6 is an experimental Intenret Exchange for IPv6 only. It was started in KDDI Otemachi Building (Downtown Tokyo) with a FastEthernet switch. Now access in NTT Communications Otemachi Building, in toyama, and in NTT West Dojima 3rd Building is possible.
While it is just an experimental IX, more than 20 ISPs are connected together natively. It is one of the biggest IPv6 IXes in the world.