Yanagawa has long held a traditional event known as “hori-boshi.” As its Japanese name implies, the canals are drained of water once a year, and disinfected via exposure to sunlight. Algae, trash and other detritus is removed and the canals are cleaned. In the past, the mud that accumulated at the bottom was used as fertilizer, and made for a good opportunity to catch koi and crucian carp for sustenance.

In the river’s polluted years, Hori-boshi was all but forgotten. But it was thanks to hori-boshi that the river was revived. The first such cleaning after a decade found the canal bottom sludgy as a swamp. Wardrobes, televisions, bicycles, cars – anything short of airplanes and war tanks – were pulled from the muck. Nevertheless, once the residents came together, it only took three years to purify the canals from start to finish. The short labor was perhaps due to the pollution still being relatively shallow. Afterwards, grass carp were released into the canals, eating the algae and making the river even cleaner. As a result, tourists returned for canal cruises again, and the sight of newlyweds boating along the river returned once more.