Inasu is one of Wado's core principles, which means to change the direction of the attack.
Have a look at the image below. A represents the initial position while B represents the desired position. In other words, A could be the Hikite position and B could be the position of the fist when the punch is completed. If B is where your face is, or any part of your body you will be having a bad day. This is where Inasu comes in.
Inasu, meaning to change the initial direction, is the event where you manipulate the trajectory and change the intentional outcome. As you can see from the image, at X, the trajectory is changed from B to B2, making sure that the attack misses its target.