*Here I am using Photoshop, but you can use GIMP to make and measure your lines.
So Rintare is going to be Ryuu, so we are going to scale the item to Rintare. Since we actually don't know the height of Ryuu (which is actually irrelevant since we're scaling it ourselves),
So first, I measured the height of Ryuu in pixels (px). It came out to be 1798px. I then measured the length of the staff at 1019px. So with these two measurements we can begin to create our ratio of inches per pixel. This way we can convert anything we know from pixels to inches. Rintare's height is 5 feet and 6 inches = 66 inches. So now we know thet 66 inches = 1789 px. if we do 66/1789 = .0367in/px. Now we can apply this ratio to all our lines and get the measurement in inches. So in the end we get that the staff is 37.4 inches long.
After all these calculations, I wanted to see what the stick's shape was like. So I took the above screencap from the anime and redrew and colored the weapon to get the larger picture. I included the shading given in the anime in order to get a feel for the roundness/edging of the weapon as well.
To get a feel for the width of the whole thing, I went ahead and applied our ratio to the thinnest and largest part of the weapon. The item itself seems a little unreasonable if I'm to make it out of wood, so I will be adjusting them so that it is structurally sound.
That's the planning process! In part 2 I'll go over the actual creation. Stay tuned.