Yasudagawakakou (Yasuda Rivermouth)

Yasudagawakakou (Yasuda Rivermouth) is an exposed reef/rivermouth surfing spot in the Yasuda area where the Yasuda River meets the ocean. It’s described as rare and fickle—sometimes breaking—because the setup depends heavily on sandbar alignment at the river mouth. When the sandbar and swell/wind line up, the wave can deliver fast, hollow character and occasional barrel-like sections. The best conditions are repeatedly tied to a south (southwest-inclusive) swell combined with offshore wind from the northeast (north/east/northeast are also cited as working). With the wind offshore, the surface tends to clean up, improving rideability. Low tide is consistently identified as the optimal tide position, and the wave is described as capable of holding size during typhoon events. Hazards are significant: the break area features rocks and boulders, and strong river currents can be present after heavy rain or during large swells. Localism is also flagged as heavy, with an emphasis on strict respect for lineup etiquette—waiting your turn and avoiding dropping in. There’s no dedicated lifeguard presence and rescue availability is noted as none. In terms of timing, August is the primary best month across multiple references, with typhoon-season influence noted for late summer into early autumn. Crowds are reported as sometimes crowded (and can become intense when the wave is working), so planning around swell working windows and respecting other surfers becomes part of the success of a session.