The circumstances of Nishi's death are unknown and subject to competing theories. One theory is that he found himself in the midst of enemy forces on the morning of March 21 and was killed by machine gun fire while moving to the regimental headquarters. Another is that he and his aide killed themselves with their pistols near Ginmyōsui or Futagoiwa. Yet another is that he was burnt to death by American flamethrowers on March 22, or that he and several subordinates carried out a final assault and were killed in action.