Seaweed Jelly or agar(-agar)
One winter day in 1658, Tarōzaemon, the owner of an inn named Minoya in Kyoto served a Daimyo a Tokoroten (a product made from seaweeds) dish. But probably he prepared too much of it, he had to dump the remaining outdoors, which froze at night, melted in the day and turned into a dry state after a few days. For curiosity, he picked up this dry matter and boiled it in water, then lo and behold! — he got a fantastic food product — more refined and less seaweed-smelly than the original food, which was eventually named Kanten. Due to its smooth, jelly-like characteristic, it’s widely used as an ingredient for Japanese sweets such as Yokan (a jelly-like item) and Mitsu Mame (fruit slices and dumplings mixed in black syrup). A Kanten jelly prepared by mixing beaten egg white is specially called Awayuki Kanten (light snow Kanten) and features a mild sponge-like texture. By the way, Kanten is also used for healthy diet products thanks to its low-calorie properties.
(Photo: Awayuki Kanten made by adding beaten egg white.)