The back is something that only the person can't see. It is exposed to the gaze of others unprotected. So, she says, "When I touch it, I feel like I saw something I shouldn't see, and I feel like guilty." The invisible back is like your death that you can never experience. The existence of "I" has already been surrendered to the world of enlightenment in that sense. From her collection of essays "Warm An Egg Under The Black Cloud."
"December 28 2019
from “Oriori no Kotoba” by Kiyokazu Washida, The Asahi Shimbun"