Who invented ninjutsu?

It's suspected to be Kumawaka. He was getting revenge on Homma Saburo for killing his father,so Kumawaka sneaked in Saburo's house and killed him while Saburo was asleep using Saburo's weapon since Kumawaka didn't have one. That day Kumawaka was declared the first ninja assassin for his trickery,stealth,and agility.

though i am the first crazy ninja cause i think tacos taste good do u???