The Kuji-Kiri are the Ninja's Nine Levels of Power. They are 1. Rin - Strength of mind and body. 2. Kyo - Direction of energy. 3. Toh - Harmony with the universe. 4. Sha - Healing of self and others. 5. Kai - Premonition of danger. 6. Jin - Knowing the thoughts of others. 7. Retsu - Mastery of time and space. 8. Zai - Control of the elements of nature. and 9. Zen - Enlightenment.
Shô Kosugi is an actual Ninpo practitioner and was also the movie's technical advisor and fight co-choreographer. Kosugi starred in numerous other 1980s ninja movies and appeared in each of the films in Golan-Globus' Cannon "Ninja" series but playing different characters.
Despite being the third and final entry in the Ninja trilogy, this film has nothing to do with the first two films Enter the Ninja (1981) or Revenge of the Ninja (1983), despite the fact that they all star Shô Kosugi (but playing a different character in each film).
The third and final of three "Ninja" movies in the Golan-Globus Cannon Ninja trilogy. The first and second films were Enter the Ninja (1981) and Revenge of the Ninja (1983). All three films were unrelated in terms of story. Cannon also went on to make American Ninja (1985) which spawned its own franchise which went to five movies.