Japanese mayonnaise uses rice vinegar for its ingredients, so it has a deeper yellow color to it.
Compared to standard American supermarket mayos, it uses soy-based vegetable oil, apple or rice vinegar rather than distilled vinegar and egg yolks rather than whole eggs and has a tangier flavor to it.
They are bottled in soft plastic tubes and the most famous brand is the Kewpie Mayonnaise.
Since rice vinegar is also an ingredient for sushi rice, this mayonnaise is a natural match to be used for making spicy sauce for fusion type sushi rolls. Japanese mayonnaise can be used alone to dress chopped scallops along with scallions as well.