This video, titled "Baikamo｜A Species Endemic to Japan｜Shinonsen] 4k" (バイカモ　日本固有種 【新温泉町】4k), was released by "e-eizo.com" (e映像制作.com).
This video was filmed at the Takimi River in the Shinonsen area, northwest of Hyogo Prefecture.

There are hardly any spots in Japan where so many Baikamo are in full bloom.
Baikamo is an aquatic plant belonging to the buttercup family and blooms underwater and on the surface of the water.
Throughout the summer, Baikamo produce many pretty plum blossom shaped flowers.
Baikamo only bloom in areas with clear water or close to headwaters.
It is a plant that grows in cold water and can be found in Japan in the mountains of the Tohoku and Nagano regions.