Nagasaki was historically the center of Catholicism in Japan. In fact, the city was once known as the Rome of Japan and was seen as the center from which East Asia could be evangelized. St. Mary's Cathedral in the Urakami district of Nagasaki was the largest Catholic Church in East Asia. Until, that is, the second atomic bomb dropped by the United States on Japan exploded over the city of Nagasaki on August 9, 1945. The targeted area was just five hundred meters away from the cathedral. The cathedral, along with the entire district, was destroyed, as was the center of Catholicism in Japan.
The following articles describe the impact of the atomic bomb on Catholicism in Nagasaki:
The first one focuses on the miraculous survival of priests dedicated to praying the Rosary in Hiroshima, also alluding to a similar miracle at Nagasaki.
The Jesuit Priests Who Survived Hiroshima
The second describes the historical development of Catholicism in Nagasaki and offers a spiritual reflection on the destruction visited upon Catholicism there.
The Catholic Holocaust of Nagasaki — "Why, Lord?"
The third article describes the history of a statue of the Virgin Mary, pictured above, that survived the bombing of the cathedral.
1,000 Torch Bearers Carried the Virgin Mary in Nagasaki. Here's Why
The next artcile focuses on survivors the bombing of Nagasaki, who have shared their stories.
Catholic atomic bomb survivors from Nagasaki share personal stories
The last entry is the Wikipedia article on Takashi Nagai, a Catholic physician, who survived the attack on Nagasaki, after which he led a life of exemplary prayer and service, earning him the title Servant of God, the first step toward sainthood.
The Life of Takashi Nagai