Fumasatsu (風摩殺, Fumasatsu; literally: Wind Rasp Killing) is a fighting technique.
The user of the technique has to hit his opponent quickly on the side of the jaw with their palm, this causes the mandible to dislocate. It can be used as a surprise attack, when the opponent is looking the other way and turns to attack, for example.
Orochi Doppo is the only character who mastered this technique and used it against Yuu Amanai during the Maximum Tournament Saga. Anyway, it is shown that Izou Motobe knew the name and operation of the technique, but it is unknown whether he ever learned that move.