Haranojo was the name of a castle used in the 1637 Shimabara Rebellion, an uprising of Catholic believers who were terribly oppressed and farmers who were burdened with a heavy land tax. The insurgent troops were defeated by the Shogunate’s army, numbering over 100,000, and nearly all of them were killed. The number of dead is sometimes said to have been 27,000, and at other times, 37,000. Funakoshi, who was himself a Christian, visited the ruins of the castle one spring day and tried to envision the slain Christian warriors “rising up like ghosts as they were bathed in the wan light of the moon that night after the rain had stopped.” He created this work based on this impression.