My oldest son chose to be a ninja this year for Halloween! His request was to have a blue belt and a thing that could put all his tools in, and a dragon on it. So I got to work. I picked these three capes up at the goodwill store for $1.50. Can't beat that. I only ended up using two of them. The third I am going to use for the bat costume...
Take your cape and lay it flat. I then folded over the front of the cape at the seam. The seam will then serve as the side seam in your pants. You pretty much are just skipping a step in the pant making process. Which makes it so much easier, and faster.
If you know anything about real ninja's...lol...there pants are tighter at the ankle and are a little looser towards the top. To make my pant piece I measured from his hip to his ankle and then added 3 inches. This will be the long side of the piece below. And then I measured his ankle and halved that measurement. That is the shortest length you see coming off of the long side. This is the ankle opening. Then the other side coming off of the longest seam, which is the waist, is half of their waist measurement. Then coming down from that is the measurement from the bellybutton to just above the knee. I measured mine three inches above the knee. And then measure 4-6 inches across depending on the amount of hang you want in the top of the pant. I did 4.5 inches. And then cut a diagonal line connecting this end to the ankle end. (I sure hope that made sense...maybe next time I'll draw it out...) You need two of these pieces. Note. The folded line with the seam is the long edge.

Turn the pieces so they are right side in and put the two pieces on top of each other. Sew the sides together. This is the side that you measured from the belly button to above the knee.

Then put the seam you just sewed in the middle now on both sides and lay the pieces flat like pictured below and sew up the legs, across the crotch, and down the other leg.

Fold the top down and sew a 1 inch casing, leaving a small opening. Feed your 3/4 inch elastic through it, and sew it closed. I also had my son try them on and it was too lose in the crotch area so I rounded mine out a little bit instead of straight across. It kind of looked to MC Hammer for me than Ninja!

Now for the shirt. I took one of my sons long sleeve shirts and used it as a pattern. I cut two of the sleeve pieces by laying it out like below.

And then I did the same thing with the front and back of the shirt. Next I sewed the sleeves on to the front and back of the shirts.

Fold the sleeves in half and line up the front and back piece and then sew from the bottom of the shirt clear to the end of the sleeve. Do this on both sides. And yes, my picture is blurry. Sorry about that.

Take the hood from the cape.

Round the top part and trim off the square point. And then measure to the length you need it. I put mine on my son and then cut it off an inch below his shoulder.

Here in this picture I have placed a pin at the center back of the shirt which is right sides out. The hat is above and the seam line to the left is the center of the hood.

You are going to pin the right side of the hood to the inside of the shirt starting from the middle out. Go all the way around the neckline until you run out of hood in both directions.

It will look like this. There will be about a 4-5 inch space in the front of the shirt.

Sew around the edge to attach the hood. Now have your son try on the shirt and place a pin on both sides above his nose where you want the face piece to be.

Cut a square that will fit in the area. Mine was 7.5 inches square.

Attach it to the inside of the hood on one side. The inside of the hood is to the left. So the edge of the square is facing into the hood.

Fold it across and do it to the other side of the hood. Please note, you are looking at the inside of the hood, so the shirt is inside out.

Turn the shirt right sides out and sew across the square piece attaching it to the neckline. Their might be some extra fabric like mine has below. It's okay. You can leave it or just trim it after you sew the line.

Turn it right sides out. You can see the line we just sewed at the bottom of the square face piece and the top of the neck.

You can slide your hand down and this piece should lift up. This is what covers the nose and mouth.

I then screen printed a dragon onto the front.
Now for the belt piece. Take a rectangle of the fabric that is 3 inches larger than the waist measurement and double the height you want the finished belt to me. Mine is 8 inches.

Fold it in half and sew around the edges leaving one edge open. Turn it inside out and sew it closed.

I then layered the two short sides on top of each other and sewed a very fast and uneven rectangle to hold them together. Note, you can also sew Velcro here to remove the belt easier if you would like.

I then sewed two little squares of fabric in a diagonal onto the front. Sew down the two sides. These will be to place the daggers.

And then next to one of the rectangles on the side, I sewed a piece of the tie from the hood. This is so he can put in his numchucks.

Take a rectangle piece of fabric, I did mine 5 inches by 12 inches. Fold up the bottom leaving a 2-3 inch flap at the top. Sew the sides.

Flip it inside out and sew it to the bottom of the other side of the belt just above the opening to the pocket. This is to put in the chinese stars.

Have your son put it all on. And then take scraps of contrasting fabric and tie it around his upper arms, waist, and lower legs.

And he is good to go...Except...I was informed by the man of the house he needs one long sword.

So I will be picking that up today and adding it to the attire...

The boy is pretty proud of his Ninja costume...because it looks so real, he keeps saying.

As if he knows what a real ninja looks like...

But then again, maybe he does. He seams to have all the ninja moves...
Stay tuned for the bat...It's coming soon!!! If this tutorial was way to confusing. I am so sorry. It's a little more difficult one...after these costumes are complete...I will be back to my regularly scheduled tutorials and crafting! Hurray...I can't wait...