So-called Sashimi knife is what's referred as Yanagiba (willow blade), because of it long thin shape. Yanagiba is designed solely to cut fish, specifically to slice to make sashimi. For this reason, the blade is sharpened only on onside, "Single Bevel", leaving the other side flat so that the edge of the sashimi piece will have straight edge, which Japanese considered to be more appetizing. The reason for a long length is to slice the fish with one stroke. Yanagiba comes with several different length - 240mm、270mm、300mm and 330mm. The longer the blade is, harder to master the knife. For a beginner, 240mm or 270mm is a good length to start. Masamoto is one of the most popular Yanagiba makers in Japan and is very popular among sushi chefs both in Japan and US. Here on their website they talk about a different type of knives including Yanagiba. Using Yanagiba When using Yanagiba to slice fish for sashimi, you need to "pull" your knife toward you to avoid breaking fish meat. Because fish meat is soft and delicate, if you push your knife to cut fish like meat or vegetables using too much force, you will break its meat and lose delicate flavor of sashimi. Learning how to sharpen your yanagiba is also a very important part of using the knife. When I was working at a sushi restaurant, I sharpened it every day before I start my shift so that the knife retains the optimal sharpness to produce nice straight sashimi pieces.
Where to get some Yanagiba and Japanese Knives in San Francisco Bay Area
1640 Palm Avenue, San Mateo, CA 94402
They have more Japanese knives than I've ever seen at any store in US. They carry Kikuchi Japanese knives and they make excellent Sashimi knives. They also specializes in knife sharpening.
593 Guerrero Street, San Francisco, CA 94110
Small, but carris good amount of Japanese knives. They offer knife classes as well.
1698 Post St, San Francisco, CA 94115
Japanese hardware store located in Japan Town, San Francisco.