It is. It's a spin-off, and if you look that the only SF game that existed before this is the original shitty one, it was after this that the franchise became 2D fighter primarily.
One of the most criminally overlooked games ever. Has to be one of the best action games on the NES. I'm completely convinced that if this game had come out on the Super Nintendo and hadn't been presented as a sequel to Street Fighter it would be held as an all-time classic.
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