[1] Nagai was born in Matsue and grew up in the rural area of Mitoya, raised according to the teachings of Confucius and the Shinto religion.

He began to read the Pensées which influenced his later conversion to Christianity and boarded with the Moriyama family, who for seven generations had been the hereditary leaders of a group of Kakure Kirishitans in Urakami.

Takashi learned that the construction of the nearby Immaculate Conception Cathedral in Nagasaki was financed by poor Christian farmers and fishermen.

He slept without drying himself and found the next morning that he had contracted a disease of the right ear (signs of meningitis), which made him depressed and partially deaf.

Nagai made a quick diagnosis, telephoned the surgeon at the hospital and carried Midori there on his back through the snow.

Eventually, Nagai's spiritual progress took a decisive turn when he thought about Pascal's words:"There is enough light for those who only desire to see, and enough obscurity for those who have a contrary disposition.

Takashi became a member of the Society of Saint Vincent de Paul (SSVDP), discovered its founder, Frédéric Ozanam, and his writings, and visited his patients and the poor, to whom he brought assistance, comfort and food.

[12] On 7 July 1937,  the same day as the birth of his first daughter Ikuko, the Second Sino-Japanese War broke out and he was mobilized as a surgeon in the service in the Medical Corps of the 5th Division.

[6] This disease was probably due to his exposure to X-rays during radiological examinations which he performed by direct observation, since films were not available during the war period.

At the time of the atomic bombing, Dr. Nagai was working in the radiology department of Nagasaki Medical College Hospital.

He received a serious injury that severed his right temporal artery but joined the rest of the surviving medical staff in dedicating themselves to treating the atomic bomb victims.

[15] He returned to the district of Urakami (the epicenter of the bomb) on 15 October 1945 and built a small hut (about six tatami) from pieces of his old house.

[1] In 1947, the local Society of Saint Vincent de Paul (SSVDP) built a simple two-tatami teahouse-like structure for him.

Nagai named it "Nyokodo" (如己堂, Nyoko-dō to, literally "As-Yourself Hall", after Jesus' words, "Love your neighbor as yourself."

Takashi gave a speech filled with faith, comparing the victims to a sacred offering to obtain peace.

[18] In 1948, he used 50,000 yen paid by the Kyushu Times to plant 1,000 three-year-old sakura (cherry) trees in the district of Urakami to transform this devastated land into a "Hill of Flowers".

[18] On 1 May 1951, he asked to be transported to the college hospital in Nagasaki so that the medical students could observe the last moments of a man preparing to die from leukemia.

He prolonged the day of hospitalization to wait for the statue of Our Lady, a gift from the Italian Catholic Medical Association.

[21], with the purpose of annually awarding individuals and/or organizations, both domestic and overseas, for their contributions to world peace through the improvements and developments of medicare for hibakusha and related social welfare.

[23] Shunichi Yamashita, the director of the center,[24] who was appointed as an adviser to Fukushima Prefecture on radiation exposure after the Fukushima nuclear accident,[25] wrote:"I myself [am] just a younger alumnus of the same university, I found Nagai Takashi Memorial International Hibakusha Medical Center at Nagasaki University Hospital.

Furthermore, by founding the Takashi Nagai Memorial Nagasaki Peace Award as an international activity of Nagasaki Association for Hibakushas' Medical Care, I am making an effort in order to honor the doctor for a long time succeeding the last wishes of those who [know] the doctor like the late Soshino Hisamatsu, the director of [the] nursing service department.

"[29]Nagai left behind a voluminous output of essays, memoirs, drawings, and calligraphy on themes including God, war, death, medicine, and orphanhood.

His intensely personal meditations are often addressed to his children or to God, and he works out his own spiritual issues on the page as he writes in a visceral and uncensored prose.

Nagai's more technical writings, in the Atomic Bomb Rescue and Relief Report (Nagasaki Idai Genshi Bakudan Kyuugo Houkoku), were discovered in 1970.

[30] NOTE: Dates of publication do not reflect the order in which the works were written; some were published posthumously, and all have been subsequently re-compiled for the Paulist editions.

[31] Nagai's "The Bells of Nagasaki" was used as the basis for a film of the same name produced by Shochiku movie studios and directed by Hideo Ōba.

[34] The film is directed by Ian and Dominic Higgins and stars Leo Ashizawa as Dr. Nagai and Yuna Shin as his wife, Midori.