Origami is the Japanese art of folding paper into various shapes without cutting or tearing the paper. An origami sword is just one design among thousands of possible shapes a paper can take in origami, all stemming from a few basic folds. It is best to use special origami paper --- square pieces of paper specifically designed for origami folding --- when attempting to make these shapes. It is a very simple process to construct an origami sword.
Valley-fold the origami paper in half horizontally, then unfold the paper and valley-fold it vertically.
Unfold the paper, then turn it over and valley-fold it diagonally from top left to bottom right.
Unfold the paper again and valley-fold diagonally from top right to bottom left. Unfold the paper one last time. You should now have an "asterisk" pattern on the paper, two lines going straight vertically and horizontally and two lines going diagonally so that it looks like a large "X" design over a "+" design.
Rotate the paper 45 degrees so that it is layed out in a diamond configuration.
Fold the two horizontal corners inward so that the points meet in the center of the paper.
Turn the paper over and valley-fold both sides horizontally about halfway between the top and bottom points and the first angle-edge. This should reveal the tips of the folds you made in the previous step.
Valley-fold in the tips so that you now have a long six-sided "blade" with a diamond design much like would be seen on the hilt of a katana.
Make a valley-fold across the horizontal center of the second diamond, then make a mountain fold 1/2 inch below that. This will give you a much smaller diamond pattern near the bottom of the "sword."
Make two squash folds on either side of the small diamond's horizontal center. This will leave you with a smaller handle beneath a larger blade.
Make a valley-fold at the bottom of the hilt, across the horizontal center of the smaller diamond.
Make two squash-folds so that the blade folds into the size of the handle and the two lower tips of the blade come down to form the cross-guard.