from a conversation with Kobun Chino Roshi (He was a Kyudo student of Shibata Kanjuro XX)
It is about the essence of "shahin" - 射品. What are the characteristics of shahin? How do the practitioners achieve this shahin? "Sha" means shot, "hin" means something like dignity or the noble essence that is polished out by the practice.
It refers to the goal. The target becomes a mirror, and my understanding is that this "target mirror" is an accurate reflection of one's own self, one's own form called "shakei" - 射形 "Kei" means form.
Our body, limbs, bow, sinew and arrow should all be in a balanced harmony like a healthy family. The father is the strength of the bow pressed from the left side; the mother is the tension of the tendon pulled from the right side; the arrow is the child, released to grow. You shoot to release the arrow so it unfolds in space and time. You shoot so that the spirit of archery receives a visible manifestation and in addition to that to develop the invisible quality in your life: "Shashin" - 射心: "Shin" means spirit centre and soul life, and the meanings developing from it.
Shibata Sensei has said that one does not attain shahin. It is polished out from within. It unfolds naturally by itself as a feature of your own life, as the archer's own life itself. This quality can be seen not only during shooting, but also in everyday life.