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The Switch Cancel is executed by pressing the tag buttons in the middle of a combo, allowing a player to switch characters (with the exact timing for each combo varying). The tag partner will be swapped in as the current character is executing their move. Executing a Switch Cancel uses one section of the Cross Gauge.
Players can potentially use the opponent's blockstun against them, i.e. executing a high attack, then Switch Canceling and executing a low attack while the opponent is still in blockstun.