Japanese hair isn't uniform - there is no "best" shampoo for Japanese hair. There are good shampoos, but no single best.
Tsubaki has a great ad campaign going on, saying that they are the best for Japanese hair... Then Asience came out with a copy of their ad copy - designed for Asian hair, etc.
The only real difference is the ad campaigns. Any Japanese brand is designed for Japanese hair.
What type of hair do you have? That is what will make the real difference in what shampoo is best for you.