Rui-be is a traditional dish originating from the indigenous Ainu people of Hokkaido. The dish consists of seafood that's frozen, sliced just like sashimi, then served with water peppers, soy sauce, and wasabi. Ruibe is usually prepared with wild salmon, and in the past, fishermen left the fish to freeze in the snow, but they didn't wait until spring to enjoy it – they plaed the sliced pieces of fish in their mouth and let it melt – and ruibe was born.

The word ruibe means melted food and it's said that it tastes like nothing else due to its texture that's both creamy and frozen.