The Murasaki Uni (in Hokkaido we call "Kita Murasaki Uni" is a variety of long spiked Uni.
It is known as Japan's top quality Uni, with its being extremely plumb and large in size (around the size of your thumb) so it is much larger than any of its other Japanese counterparts and it is a lot creamier and sweeter with a light of texture that virtually melts in your mouth.
The color is generally pales yellow but sometimes comes in bright orange. Kita Murasaki can fetch up to around $1,000 per tray at the market.