Devils_hand
Ninshu is not the precursor to ninjutsu in the sense that it’s just ninjutsu without hand signs or mastery over chakra to the point you can do whatever you want with it. Ninshu is basically using chakra to connect to other people to share feelings and understand one another. Examples: 1) Naruto and Killer Bee fist bumping and talking in their mind space. 2) Hagoromo spreading chakra by touching others and pushing energy into them. 3) Naruto running around and slapping all the surviving ninja in the 4th war, spreading his chakra cloak to them. Ino reporting he can feel Naruto’s emotions through the connection.