This is a difficult mission so we have included a brief walkthrough for it to help anyone stuck when trying to achieve its objective. the idea is to have your ninja free fall from a great height, but the height required is much higher than you can reach within the normal field of view on screen.
to build up some height, use the Large ninja Tower and position it in some space within the arena. Next, place a stack of Metal Rocker Crates on top of each other on top of the Tower. Do this slowly as it can be fiddly and you need it to be reasonably well balanced.
Finally, drag your ninja slowly up onto the top of the uppermost crate. You should try to wait until he has stopped swaying before you lower him onto it, and give the crates a wide berth initially as he will try to grab on and may knock over your creation. Once he is stable, simply tap on the ground and he will jump off to get down, accomplishing the mission.
I don't get it