Kewpie mayo is Japanese mayonnaise. It is made with just egg yolks instead of whole eggs and there is no added sugar. It is creamier and thicker that regular mayonnaise and has a richer flavour. It is typically used for sushi, but it works very well with seafood, especially sandwiches. It can also be used in pasta salads or almost any recipe that calls for mayo when you want a richer flavour.