Oura Cathedral is dedicated to the 26 martyrs of Japan, and was built to face in the direction of Nishizaka, the place where they were crucified. The martyrs had been canonised in Rome three years before its construction, in 1862. The new church’s official name was thus the Saint Twenty-six Martyrs of Japan Cathedral.

Owing to the ban on Christianity (which was still in force at the time of the church’s construction), most Japanese people had no way of knowing that these canonisations had occurred. On the other hand, news of the martyrs had quickly spread to many countries throughout the world following their crucifixion 1597.

Soon after the executions, people planted flowers such as camellias in the spot where the martyrs had been crucified, and it became a place where Christians would pray and gather. However, the more severely prohibited Christianity became, the more the martyrdom spot faded from peoples’ memories.

Petitjean and others thought that by building a church to face the spot where the 26 martyrs were crucified, it may send a secret message to any Hidden Christians there might be and encourage them to come forward.

Inside the Cathedral, there is an oil painting depicting the martyrdoms. It was commissioned by Father Petitjean during a stay in Rome in 1869.