Today, I found this new Japanese soft drink, Shouyu Saidaa (soy source soda). In the west of Japan, in between Honshu (the biggest island) and Shikoku (the smallest of four main islands of Japan), there is a little island called Shodo Shima (小豆島). This island apparently produces good soy source (shouyu/ 醤油or正油) and now one of shouyu company has made soda with soy source.