Tendon

Emerged in late Edo period (early-to-mid 19th century) Tokyo, when tempura yatai stalls began offering their tempura over rice as a portable cheap meal. The originator is disputed — claims point to a soba-yatai precursor of Shimbashi's Hashizen (c.1831) and to Asakusa's Sansada (founded 1837), the latter being the oldest surviving tempura shop in Japan. Sansada's founder Sadakichi first set up his tempura stall in Nihonbashi's Ningyocho, not Asakusa. The dish belongs to Edomae cuisine — tempura batter and tentsuyu both rely on dashi from Tokyo Bay's fish, and the speed-eating culture matches Edo's working-class pace.

Late-Edo Tokyo street food — Sansada in Asakusa (founded 1837) was already plating tempura over rice by mid-19th century. Tentsuyu has to hit the bowl at the moment of plating; a tendon you eat slowly stops being tendon.

A bowl of rice topped with two or three pieces of just-fried tempura — typically a head-on shrimp, a slice of kabocha or kakiage — drenched in tentsuyu (a sweeter, thicker dashi-soy-mirin sauce than the dipping kind). The batter goes from shatter-crisp to softened at the rice contact point. Eaten in 5-7 minutes before the batter fully sogs. A tendon you eat slowly stops being tendon.

Tentsuyu must be applied at the moment of plating — not from a bottle, not in advance. Shops dip each tempura piece briefly in hot tare and drape it over rice; the heat-thinned sauce penetrates the batter unevenly, which is the textural point. Soaking tempura fully in cold sauce produces uniform soggy mush. The tempura oil also matters: pure sesame for old-Tokyo shops, blend for modern — sesame oil's smoke-darkening is what makes Edomae tempura visibly browner than Kansai's.