Known as the King of the River, Daisuke of the Salmon marks forbidden periods and seasonal rites during the salmon run. On set dates—such as the fifteenth of the Frost Month and the twentieth of the Twelfth Month—Daisuke and his consort Kosuke are said to proclaim in loud voices. Anyone who directly hears them dies three days later, so riverside communities kept those days as no-fishing days, ringing gongs, singing, and pounding rice cakes to block out the sound. In tales along the Shinano River, a powerful elder who forces taboo-breaking meets a water authority in the guise of an old woman and dies suddenly with the run’s onset, embodying awe of nature and adherence to proper conduct. The old woman is read as a personified river spirit or Daisuke’s avatar, though never revealed outright. The name varies between “Daisuke of the Salmon” and “Daisuke the Salmon,” and his wife is called Kosuke. Recorded from the early modern period in surveys and folktale collections, this motif spreads across the salmon culture zone of eastern Japan beyond specific locales. Creative variants are few, and the core points—voice, dates, taboo, and fatal retribution—remain consistent.