We made paper koi kites in kids' drawing class. The Japanese Cherry Blossom Festival in Washington DC is probably over by now, their cherry trees have probably dropped all their petals. In Maine our crocuses have only just 'gone by'. I did see forsythia out on the way to the library for class.
My whiteboard drawing demo shows the basic design idea. Fold a rectangular sheet of paper, (copy paper), in half the long way. fold the long open sides over twice, about 1/4" each time, as if you are rolling up but crease well along the folds. This helps the paper stay fastened together somewhat. Then fold in the mouth end edge about 1/4" all around - like you would do with a paper bag you want to use for garbage, (but you fold the edge in, not out.)
After you have decorated both sides of the fish, cut a little slit in the belly across the folded 'seam', about 1/2". You will stick your 'stick' up through so you can have your koi fish on a stick. I made colored paper sticks out of long 1/4 sheet strips of the copy paper by folding them over several times the long way. They need to be creased well. They won't lie flat but with that many well creased foldovers they become quite stiff. At one end bend a portion over to form the shape of a T pin. You will insert that part in the slit. The T head needs to be longer than the slit and turned a bit at an angle to the slit. That keeps it closed inside the kite.
Open the koi at the mouth so that it has a tubular form rather than being flat.
Make more koi kites and experiment with other ways to fasten sticks and strings to it. They can be fastened by strings at the mouth to a stick.