This is based on a legendary episode included in "Urabon-kyo" (translated by Hogo JIKU and Zhu Fahua who lived in the Western Jin era) and "Honhobon-kyo" (translated by Shitsu in the Eastern Jin era), or on the legend where Mokuren Sonja held a memorial service for his dead mother who had to live in Gakido (the Buddhist hell of starvation).
これは『盂蘭盆経』（西晋、竺法護訳）『報恩奉盆経』（東晋、失訳）などに説かれる目連尊者の餓鬼道に堕ちた亡母への供養の伝説による。