The Sea Eel in Japan differs from what is served in restaurants outside of Japan. The sea eel is 99% frozen when transported and once defrosted before serving. It warmed in a toaster oven and then the chef swipes the eel with a sauce named Tsume, a sweet sauce that is made from a reduction of the water juice from boiling sea eel. The sauce is thickened and reserved for some fish that require sweetness. In the video you see the chef preserving the juices for the Tsume.