Yan Guimen, who practices magic, has a strange lesson that every second-year student must practice regularly.
Hold Yuan Shouyi, clear away distracting thoughts, let the energy race in the mind for a quarter of an hour, and then "pull it out of the body."
However, this excrement-like by-product of practice will carry the practitioner's thoughts for that quarter of an hour and can be read by anyone.
Everyone named this thing "Vitality Log".