I'm not sure exactly what to call it, perhaps an old wives' tale or a popular misconception or perhaps even the cold hard truth, but it is commonly believed in Japan that eating eel during the summer will grant you increased sex drive and sexual stamina. For some reason this only works during summer, which is why unagi is most popular then and many stores will have discounts on unadon and the like.

I just like it for the texture and the taste. Really.