I'm currently on Chapter 7 trying to complete the Fiend Challenge in Master Ninja mode that is consists of purple cat-like ninjas who jump at you and rotate around your neck and the floating eyeballs that shoot fireballs at you. I was told that Izuna Drop is the best attack to use against those retarded ninjas but sometimes the move doesn't work. I've tried sliding the stylus down, up and up again and again but Ryu doesn't do a damn thing. I've also tried using the standard sliding back and forth attack but the ninjas keep hurting me no matter when I'm dodging or attacking. I'm not sure if I'm doing something wrong or the programmers didn't do a good job. 
 
Any tips or advice on how to beat this Fiend Challenge?