I remember having been in Japan and ate several meals of cold soba. Their cold soba broth taste like soy sauce with only a stint of saltiness; it doesn't taste like it's made of sushi type sweetened soy sauce; neither does it taste like a simple mixture of soy sauce and water.
Instead of using pre-made cold soba broth, I want to replicate these Japanese cold soba broth at home. Googling directs me to different recipes: some suggest mixing soy sauce with chicken broth (I can't recall any stock-ish taste); some suggest mixing with Mirin (alcohol in a soba broth - I don't think so..).
Does any know how to make cold soba broth or at least know the essential ingredients?