There are three types of Sahimi knives for slicing fish fillet --- Yanagiba, Takohiki and Fuguhiki.
A Sashimi Knife, for cutting and filleting fish or ham with a pull stroke. Slim blade in the shape of a willow leaf or Katana (sword). Long and Narrower blade is suitable for slicing tasks. Especially for preparing fresh, good&beautiful shape of raw fishes (sashimi). The Yanagiba is called "Shobu" and popular in Western Japan (around Osaka and Kyoto).
Square shape, longer blade of Sashimi Knife, designed for same purpose as Yanagiba. Not for slicing "Tako" (Octopus) but for making Sashimi. The edge line is almost straight, while Yanagiba knife's blade edge line is more curved towards the blade tip. The Takohiki was popular in Eastern Japan (around Tokyo).
A Sashimi knife for a specific purpose, originally designed for cutting, slicing Tessa (Blowfish Sashimi). Its blade shape is similar to Yanagiba, but has narrower blade width and thinner blade. It is suitable design for thinner cutting, slicing tasks.