Here are some pictures to show you the design process. The first photo shows the sketch I did with a pen, just a rough design to see how I could make the koifish and koru patterns flow together:
Below you see the original pencil sketch I designed. The koru shapes are nicely flowing with the koi fish and other surrounding tribal patterns.
Once I finished the pencil drawing of the japanese koifish, the design was traced with black markers.
I recorded the full proces of tracing, shading and coloring and made a Youtube video, so you can see how it was done:
Finally I did some digital mockups, so you can see how the tattoo looks on different bodyparts: