Thank you Peto, the red whipping is sinew and hide glue to protect the joint between bamboo and the wooden nock insert, painted red.
Jack, I'm happy you like them.
About the lashings, as you know, sinew is a wonderful material and a little goes a very long way, for lashing the leading edge of fletchings only about 4" long, or so, little strand of sinew is needed, one just needs to pay attention to lay the strand as flat as possible.
The nock isn't self, is made in the Korean style, wooden insert and sinew wrapping, I don't know the species of bamboo shafting, it comes from China, the diameter at the nock end is usually small, the internodes are quite croocked, either because of not enough straightening or the inherent nature of the species.
Apart from the feathers the whistling arrow doesn't have any Japanese features.
Thank you for your comments about the whistle, that's exactly the advice I was looking for!
I don't think I'll be changing anything to this particular one though, it's going to a new owner soon and it sounds fine already, at least to me as I don't have any other than the bought machine-made metal one to compare.
But I'm just making some new ones and will definitely pay attention to your advice now.