Act I is based on the Japanese Noh drama Atsumori, which tells the story of a warrior who has been slain in battle.
Ikuta Atsumori (生田敦盛), sometimes known simply as Ikuta, is one of many Noh plays derived from the story of Taira no Atsumori, a young Taira clan samurai who was killed in the 1184 battle of Ichi-no-Tani.