Ulva is currently called SeaWheat in the EU and is considered an important biological resource for the blue bioeconomy, and its production is being promoted. In East Asia, especially in Japan, brackish Ulva prolifera has been used as a traditional and expensive food ingredient and has long been produced by natural collection or net culture. However, in recent years, the surface seawater temperature off the coast of western Japan, the main U. prolifera producing temperate region, has been warming at twice the global average rate, causing a sharp decline in production. To compensate for the lack of supply, Ulva land-based aquaculture has rapidly expanded. The land-based aquaculture technology was developed in Kochi, southwestern Japan, and commercial production began in 2004. In the 1990s, the natural collection of U. prolifera in Kochi was 10–20 t-dry y−1, but production fell to zero in 2020, and there has been no harvest since. However, land-based aquaculture has made it possible to produce equal or greater quantities of Ulva than before. This Kochi method is spreading across the country, and it is estimated that the total production capacity will reach 100 t-dry y−1 as of 2025, based on the tank area of each commercial land-based aquaculture facility. In the near future, the Kochi Method will likely be used to commercialize other kinds of seaweed.