Unverified. When playing Hyper Street Fighter Alpha, you can unlock four secret fighting styles (S-ISM's) not included in any of the Alpha Series games.
When selecting a character choose the Alpha3 version and "Normal, Mazi, Saikyo, and Classic" will appear. To choose an "S-ISM" (or secret style), move the cursor to one of the four options. Press and hold START, tap left or right once to make highlight cursor disappear and then select it.
Normal S-ism: Characters adopt the play mechanics of the Darkstalkers game engines. Advancing guard, and chain combos included.
Mazi S-ism: Characters operate much like Street Fighter III. Parries and the ability to flow into super combos from special moves.
Saikyo S-ism: Increase damage capability of normal moves and lose ability to perform super combos. Chain combo system from Street Fighter II enabled.
Classic S-ism: Seemingly random mode giving characters abilities they were gifted with in other Capcom games. For example: Classic S-ism Ken plays a lot like his Versus series incarnations. Aerial Hadou-ken and super-powered Shoryu-ken. Same with Sakura. Experiment with all characters.
S-ism characters are not playable in other versions of Street Fighter Alpha. Exclusive to Hyper Street Fighter Alpha.