Ume Fermented plum paste. Usually served with sliced cucumber in maki, very sweet with a tart aftertaste. Very good for dessert and to clean the palate. Uni Sea Urchin. If you are lucky you won't like it, if not you have just developed an expensive habit.
Lobsters eat sea urchin as a mainstay of their diet.
Wasabi Japanese Horseradish. This is the small lump of green stuff that looks sort of like clay. Best done in extremly small doses. Not related to American Horseradish except by name.