In Japan, soy sauce is typically made from a mix of both soy beans and wheat. As soy beans ferment, they oxidize and become dark in color, giving the soy sauce we think of as "regular" soy sauce its deep, dark brown color. But if you use a higher proportion of wheat, you wind up with a soy sauce that's lighter in color. That's how you make usukuchi—the Japanese name for light soy sauce. While dark soy sauce is made with around 15% wheat, light soy sauce is made with about 40% wheat, which gives it a golden, caramel color.
The "light" in the name refers only to the color of the sauce, not to the sodium level or the flavor. On the contrary—of all Japanese soy sauce types, light soy sauce is by far the saltiest in flavor. As such, it's better treated as a seasoning while cooking than as a sauce for dipping. It's great added into broths, stews, and braises.
This light soy sauce comes from Suehiro, a company that’s been making soy sauce since 1879. It packs a powerfully salty punch. It’s particularly good in broths for ramen or soba noodles. And while it may not be traditional in Italy, I also like to add a bit to mushroom risotto to give it a little extra umami oomph.