The original Mosuke, a street vendor, began making dango (soft rice-flour balls) in 1898, back when the fish market was in Nihombashi. Now on its third market, Mosuke Dango still serves its famous shōyu dango (with soy-sauce glaze) and tsubuan dango (made from chunky azuki-bean paste), but with the addition of a cafe eat-in space (matcha ¥500).
Mosuke Dango closes the same days as the market, so check the market schedule online.