Fold a sheet of paper in half lengthwise and crease it sharply
Unfold it
Fold both long edges toward the center crease
Fold the paper in half again along the center crease
Fold one end diagonally inward to form a pointed tip
Fold the sides of the tip inward to sharpen the shape
Continue folding the body lengthwise until it is narrow and firm
Make a second narrow folded strip for the handle
Insert the handle strip into the open end of the blade section
Wrap the handle tightly around the base of the blade
Fold any loose paper edges inward to secure the shape
Flatten and sharpen all creases
Repeat the process with another sheet if a thicker kunai is desired