In unagi’s story, a culinary tradition and a marketing legend are braided together; the Japanese love both, and tell both.

The tradition: on doyō no ushi 土用の丑の日, the day that falls in the most oppressive stretch of summer, Japan eats eel, for belief holds that unagi cures summer fatigue. The legend runs like this: in the eighteenth century, an eel shop with failing business asked the celebrated scholar Hiraga Gennai 平賀源内 for help. Gennai wrote a one-line sign for the door: today is the Day of the Ox. The wordplay joining the first sounds of ushi and unagi caught on so completely that the custom spread across the country. No document can prove it; but the Japanese will not give up counting it as their history’s first advertising campaign.

The taste itself needs no legend. In the kabayaki 蒲焼 technique the fish is opened, softened with steam, and grilled while being dipped again and again into sweet tare; each layer darkens the caramel. The first dedicated unagi houses entered the records in 1777; for two and a half centuries, no one has managed to stay indifferent to that smell.

Over warm rice, a smoky, sweet, velvet depth: still good for summer fatigue.