Ninjutsu is a self defence system designed to keep you out of harms way. It is not for personal gain, to harm or injure people, it does not make you lose weight, gain muscle, etc etc, its a martial art designed to keep you safe. Its been tried and tested for hundreds of years, sometimes in war torn feudal japan. It does have elements of spying, strategy and doing ninjery things but all in the common goal of surviving and winning. If you come to ninjutsu for any other reason that to learn self defence then you will not be successful.
Ninjutsu is not about
violence, being a hard man or hitting people, being nasty or harming people, its many things but not these.
For me its self discovery, mental recharging, spiritual refinement, learning to survive and win in today's challenging society.
Just my humble opinion.