Igisu is a traditional seaweed dish found in coastal communities along the Seto Inland Sea and enjoyed in parts of Tottori Prefecture. It is made from a seaweed known as igisu-gusa, also called ego-nori in some regions. The finished dish resembles tokoroten, a jelly-like food traditionally made from tengusa seaweed, but there is an important difference: igisu is prepared by simmering the seaweed until the entire plant dissolves.
The result is a naturally set, jelly-like dish with a smooth texture and a subtle aroma of the sea. Although its appearance can resemble Japanese sweet bean jelly, its flavor is distinctly savory and marine.
Igisu-gusa is collected from the coast and carefully dried under the strong summer sun. During preparation, unwanted seaweed and other impurities are removed. The seaweed is washed and sun-dried three or four times until it turns a creamy color, after which it can be stored for later use.
The seaweed itself is fine and threadlike, with tips that curve like hooks. It grows attached to the branches of other seaweeds, such as hondawara, and can reach around 20 cm in length. It is found along the coast in spring and grows abundantly through summer and autumn, with landings at fishing ports in central and western Tottori.
The traditional harvesting season for igisu-gusa is described as spring, particularly April and May, when seaweed washes ashore. Drying and cleaning the harvested seaweed is an important step in preserving it for use throughout the year.
Dried igisu-gusa is first rehydrated and then simmered over low heat until its fibers dissolve and the mixture becomes smooth. Traditionally, rice-bran liquid or the water left over from boiling soybeans may be used during cooking. The mixture is then poured into a container and left to cool until it sets naturally, without the need for added gelling agents.
Igisu can be served simply with vinegared miso sauce, vinegar and soy sauce, or mustard soy sauce. Ginger soy sauce is another option, and sesame seeds may be sprinkled on top. Some variations are seasoned with broth and additional ingredients before being cooled and set. It can also be enjoyed with dressing or, for a sweeter variation, brown sugar syrup.
The key to making good igisu is to simmer the seaweed until its fibers have dissolved completely, producing a smooth, even texture.
Igisu has a long history in Japanese food culture. It is said to have been presented to the imperial court as a tribute as early as the Asuka and Nara periods, from the sixth to eighth centuries. Related dishes, including igisu-dofu and ego-neri, are also found in other parts of Japan.
Because it is made from plant-based ingredients, igisu has traditionally been served as part of Buddhist vegetarian cuisine. It is also associated with festivals, seasonal celebrations, and important family occasions, including New Year gatherings and memorial services.
Igisu is valued for its distinctive combination of a silky texture and a gentle taste of the sea. It is also a low-calorie food containing dietary fiber and minerals. For travelers interested in discovering regional Japanese cuisine beyond the familiar dishes, this traditional seaweed specialty offers a fascinating glimpse into the ingenuity of coastal communities and their long-standing relationship with the sea.