costco的万字，是天然的, but it is a low grade 天然酱油

It is too salty and it has preservatives.

Good ones are called Traditionally Brewed Shoyu (or Tamari).Eden Foods makes very good traditionally brewed Shoyu.
Taiwan maker 味全 is also very good. I compared it with 金兰. I think 味全纯酿酱油 tastes better than 金兰鼓舌酱油. You can find 味全纯酿酱油 in Ranch 99.