I think when Japanese are asked about a folk song they remember, almost everyone will probably answer with this song. Kaguyahime（かぐや姫....Princess Kaguya）is arguably the most famous folk band that ever existed in Japan, and "Kandagawa" (The Kanda River) is their biggest hit. Kaguyahime, which was named after the classic 10th-century folktale of a moon princess found in a bamboo stalk as a baby, has had several reunions over the decades, but their first run was in the first half of the 1970s.
The song, released in September 1973, was written and composed by two members of the band, Makoto Kitajo（ 喜多条忠）and Kosetsu Minami（南こうせつ）...the latter having sung it as well. In the lyrics, Minami portrays a woman who sings her soft admonitions to her boyfriend (reportedly Kitajo in his college days) while the two of them lived in a small ramshackle room by the Kanda River. It struck a chord with listeners as it stayed at No. 1 for a total of 7 weeks (from late October to late November, and then a cameo appearance in December). It also became the No. 6 song of the year and earned the band an appearance in that year's Kohaku Utagassen. It sold 1.6 million copies. The single also appears on the album "Kaguyahime Third", which had been released a couple of months earlier than the single.