River eel is often eaten among Japanese. Especially, on the day of the ox in midsummer, people gang up to buy river eel. It is said that river eel is good for suffering from the summer heat. And there are a specialized restaurant for eel.
Originally, river eel has been eaten for a long time. In Edo Period, people became to eat river eel very often because a lot of eel can be seen by land reclamation. It was food for working person and much more reasonable.
It is recently that people eat it in the way such as grilled eel and spicy broiled eel bowl.
Here is the popular restaurant for river eel in Tokyo.