From Sega Retro
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Yonezawa (ヨネザワ) was the Japanese toy maker. Yonezawa PR21 (also known as Party Room 21) is their video game label. They created Family Computer and Super Famicom games during the 1980s and the 1990s. Their golden years consisted of games released between the year 1989 and 1994. Their most notable titles during their years of production were the Famicom game Battle Storm and the Super Famicom game Super Hockey '94.
During the 1994 fiscal year, the company published a range of software for the Family Computer before Yonezawa was bought by Sega. After the buyout, the company changed name to Sega Yonezawa, which it was known as until it was merged into Sega Toys in 1998.