From Sega Retro
Sony Imagesoft was a video game developer and publisher which operated between 1989 and 1995. It was initially established as a subsidiary of the Japan-based CBS/Sony Group (CSG) and initially named CSG Imagesoft Inc. It was renamed after Sony set up Sony Electronic Publishing in North America.
In its early years Sony Imagesoft only produced titles for Nintendo systems, but in 1992 a partnership was established with Sega to produce games for the Sega Mega Drive, Sega Mega CD and Sega Game Gear, and also for the Sega Master System in Europe.
Following a shakeup at Sony in 1995, Sony Imagesoft was merged into Sony Computer Entertainment of America (SCEA) and has since only supported the PlayStation brand.