It is made by sandwiching sashimi (fresh slices of raw fish) between pieces of konbu (kelp) and letting it stand overnight in the refrigerator, and is served with wasabi joyu (soy sauce mixed with wasabi paste).
刺身をコンブで挟んで冷蔵庫で1晩程度置いたもので、刺身と同様わさび醤油につけて食べる。