Igoneri is made by boiling igogusa (also called egogusa) seaweed until it dissolves, and then kneading and cooling it until firm. Igogusa seaweed grows by clinging onto larger seaweeds. Along the coast of Sado Island, there are many rocky shores of volcanic stone from the continental era. The unique geological features of the shore are the result of uplifted wave-cut platforms, where the seafloor has been flattened by waves and then lifted by earthquakes to the surface. A wide variety of seaweed thrives on these shores, and can be collected relatively easily. Easy access to this fresh seaweed eventually led to the creation of ignoneri.

The processed seaweed food, igoneri, is a local specialty of Sado Island. Recently, it has gained popularity as a diet food, and more and more people are incorporating it into their diets since it is low in calories and rich in dietary fiber.