Cut the satsumaimo into ½-inch-thick (13 mm) slices, then cut the slices into halves or quarters if needed. Immediately soak in water in a medium saucepan, then turn on the heat and bring to a boil. Let boil for 2 minutes and drain.
In a clean medium saucepan, mix together the 1 cup (235 ml) water, sugar, soy sauce, and salt, and bring to a boil. Add the satsum