I read somewhere that you unlock the "Ninja Blade" outfit by getting an overall completion grade of A+. Well I just got it, & my Ninja School Valedictorian achievement unlocked, but no outfit. Do you have to get A+ on every chapter?
I have the same problem. You get the Ninja Blade outfit for getting overall A+ score. I looked around and it seems that you have to replay mission 9 by selecting "launch" mission, rather than change mission and choosing it. It should unlock afterwards. I got overall A+ last night on mission 8 hard and then played 9 through selection, not just launching and i did not get it. I will try what I mentioned here tonight, so you really can't take my word for it yet. Can anyone else confirm this?