・In 1868, over 200 Christians on Hisakajima Island who confessed their Christian faith were arrested and imprisoned in a space measuring about 20 square meters. Due to cruel torture and hunger, 39 of them lost their lives, and three died immediately after their release from the jail.
・Roya-no-Sako Martyrdom Memorial Cathedral was constructed on the site of their martyrdom. Inside the church, visitors can see at a glance the size of the jail by looking at the color of the carpet.
・The Memorial Festival for Roya-no-Sako Martyrdom is held every autumn, in which followers gather from within and outside the Goto Islands to honor the martyrs and their strong faith.