It was in December of 1889 that she first set foot in Kobe. After a study of Japanese, she was sent to a college in Kumamoto City. She was to spread the gospel among the tutors and students at High School #5, which was on the present site of Kumamoto University.
She had heard of Kumamoto as a result of a severe earthquake, which made the U.K. news. Although she was afraid of going to Kumamoto she felt a calling to go to Japan. The Lord sent her to Kumamoto in spite of her fears, and she devoted over 40 years of her life to work among the victims of Hansen's disease who lived there.
April 3 , 1890 is a milestone in the history of missionary work among the victims of this disease. As it happened that day, Miss Riddell and some tutors had gone to see the cherry blossoms at Honmyo Temple, a place renowned for the beauty its cherry trees. There for the first time in her life, she saw victims of Hansen's disease maimed and begging under the trees. She was in the habit of using a book of daily readings called Daily Light , and she wrote on the page for April 3rd., "Honmyoji-first saw lepers".
She not only saw these people, but also made up her mind to devote herself completely to missionary work among them and to developing a national appeal for helping them. She started with her friends and relatives, some of whom rejected her appeal and others who offerred both financial support and respectful moral support.
Her plan began to materialize when she was able to buy 3.3 acres of land at the foot of Tatsuta Mountain. It was a good place with an eastern view of Mount Aso. There she built the Kumamoto Hospital of the Resurrection of Hope, a place to give physical treatment and psychological support to the victims of Hansen's disease.
Upon its establishment, she resigned from the Church Missionary Society in order to devote herself completely to the management of the hospital. This was only five years after she saw the people with Hansen's disease at the Honmyo Temple. Her purpose was to bring her patients up to an ethical standard of living and plant the gospel in their hearts. She gave hope to the hopeless and helped them grow mature in the Lord.
She felt that the care and cure of the patients with Hansen's disease should be a national concern. In this respect she advised the government, and visited politicians and businessmen time and again on behalf of this cause. At last the law was changed in 1907.
Miss Riddell wanted a chapel in the center of the hospital and even went so far as to design it. In 1925, the chapel, resplendent with unique Japanese features opened its doors. On the front was a framed calligraphy which said, "My house will be called a house of prayer." (Matthew 21:13) It was called Kourin Church. They prayed for Hansen's disease patients in Kusatsu and Okinawa. Kourin Church even sent missionaries to comfort and encourage them. Mr. Keisai Aoki, a Christian patient with Hansen's disease, was sent to Okinawa as a residential evangelist. He became a pioneer in medical missionary work on Okinawa.
Miss Riddell died at age 78 in the spring of 1932. She left a niece, Miss Ada Wright, to carry on her work.