The Shinobi Forever! achievement is an absolute bitch but I followed your guide for the final boss and did it second time. Just get the power up before you go to the boss, use the invincibility magic then get as close as you can and mash the attack button. I only had one magic so once I lost my invincibility I hurt him then jumped backwards missing the hair attack and got back close to him as quick as possible. Doing it that way I saved the girl with about a second to spare.
Ashes Cricket, Sega Megadrive Classics, Avatar, Madden 06, FNR 3, NBA 2K6, Cloudy, PDC Pro tour
Uno, 3 on 3 NHL Arcade, DOD, DR2:C0, Sonic&knuckles, Portal:SA, Monkey Island SE, SVC: Alex Kidd, Minecraft
Portal 2, Spelunky, Worms2:A