Hosokai Koi Farm is located in Ojiya, Niigata and is currently run by Masaru Hosokai. They specialize in breeding a variety of Koi, including Go sanke, Goshiki, Goromo, Asagi, Shusui, and other varieties.

The farm has a large raising area of 80,000 m. Masaru Hosokai, a farmer-turned-Nishikigoi breeder, is now one of the leading breeders of Niigata. He has succeeded in raising Asagi in argilliferous soil which is generally said to be unsuitable for Koi and has won various awards with them. He is currently producing many splendid Koi from Goshiki oyagoi.