The Demon Backhand Spin is one of the moves used by the practitioners of Mishima Style Fighting Karate since the original Tekken. Kazuya Mishima has his unique version called Double Backfist since Tekken 6. Baek Doo San also has this move which is named the Right Punch Back Fist. The command input is 2,2. During the animation, the character will hit the opponent with his right fist and then follow-up with a very quick (almost unseeable) spinning back fist.
When to use
Being a move that can be spammed into an unguarded opponent, the Demon Backhand Spin can give the player a very solid frame advantage much like the Demon Slayer. This is plausible because the move is more simple, easy to perform (2,2), and at the same time runs at -10 frames.