Mortal Kombat II is a pirated port of Mortal Kombat made by Cony Soft (known as Yoko Soft in this game) in 1994. This should not be mistaken for Mortal Kombat II (Hummer Team).
Street Fighter II (also known as Street Fighter II: The World Warrior) is an unlicensed port of the fighting game by Capcom, developed by Hummer Team for the Famicom and published by Cony Soft under their Yoko Soft alias in 1992.
Master Fighter VI is a port of the Street Fighter II: Champion Edition to the Famicom, made by Hummer Team & published by Yoko Soft in 1993.