What seaweed wraps the rice ball in tenmusu?

The seaweed that wraps the rice ball in tenmusu is nori.

Nori is an edible sheet made primarily from cultivated red algae, processed, dried, and pressed into the thin dark sheets familiar from Japanese cuisine. In tenmusu, it helps hold the rice together while adding a roasted, savory flavor that complements the fried shrimp inside.

The wrapper is one of tenmusu’s defining features: the dish is essentially an onigiri built around a piece of tempura shrimp and finished with nori. Depending on the shop or recipe, the seaweed may cover the whole rice ball or be placed as a strip around it, much like the wrapper on other hand-held rice snacks.

The alternatives listed are different seaweeds or sea vegetables. Hijiki is usually eaten as a simmered side dish; wakame commonly appears in soups and salads; and kombu is a thick kelp used especially for dashi stock and seasoning. None is the standard wrapper for tenmusu. Nori also appears in sushi, makizushi, and many other Japanese rice dishes.