Take a square sheet of paper. A black paper will add the perfect effect to the knife. Use thick construction paper to add weight. Fold the paper on one diagonal line, so that it is shaped like a triangle.
Now fold it in a crease right in the middle of the triangle. You will now have a smaller triangle. Unfold it. The triangle will have visible strong crease lines due to folding.
Fold one of the short sides of the triangle from the edge. Keep folding until it is all enveloped inside and makes a cone form. Tuck in any extra paper that you have inside the kunai. Use your fingers to softly press open the kunai so that it is a bit inflated. You will now be looking at the prepared tip of the kunai knife.
It is time to make the handle. Take a long piece of paper and roll it along the length so that it forms a long tube. Tape it where the paper ends so that it keeps its form and works as the handle of the knife.
At one end of the tube, fold and reverse fold a portion to make a circle of it. Use the tape to keep the shape intact. Now you will have a tube with a circle at one end.
Insert the other end of the tube into the kunai, leaving enough outside to hold on to.
Stick the tube into the kunai with tape. Make sure that it is secure and does not separate when you throw the knife. Seal the kunai with thick tape and make sure that the two parts are thoroughly intact.