Islam came to mainland China in the earlier centuries. Later it was introduced to India and Indonesia. But the northward march of Islam was blocked by the Spanish colonization of Philippines in the 15th century. Japan on the other hand has been a Buddhist country.  
Though there were a few Muslims in earlier times, the first Muslims in the recent age to visit Japan were Malays who served aboard British and Dutch ships visiting Japan in the late 19th century. Another important contact was made in 1890 when Ottomans of Turkey dispatched a naval vessel to Japan for the purpose of establishing diplomatic relations between the two countries. This ship called "Ertughrul" capsized during a storm on Sept.16, 1890 on its way back home with 609 people aboard, 540 of them were drowned.
The first Japanese to go on Haj from Japan was Kotaro Yamaoka. He embraced Islam after coming in contact with Russian-born writer, Abdur Rashid Ibrahim, in Bombay in 1909. He took his name Omar Yamaoka. He got permission from Abdul Hamid II to build a mosque in Tokyo. The approval was granted and the mosque was completed in 1938.
The real Muslim community life in Japan began with the arrival of several hundred Turkmen, Uzbeks, Tajiks, Kyrgyzs and Kazakh Muslim refugees from Central Asia and Russia in the wake of the Bolshevik Revolution during World War I. These Muslims were given asylum in Japan and had settled down in several main cities. Some Japanese embraced Islam after coming in contact with these Muslims.
When the Muslim community grew in number, several mosques were built, the most important being the Kobe Mosque built in 1935 (which is the only remaining old mosque after the earthquake disaster in Japan). There are currently between 30 and 40 single-story mosques in Japan, plus another 100 or more "Musallahs" apartment rooms for praying. 
During the WW I Japanese invasion of China and Southeast Asia many Japanese who embraced Islam returned to Japan and established the first Japanese Muslim organization, the Japan Muslim Association in 1953 under Sadiq Imaizumi. Later Umar Mita served as the second president of the association.
The authorized Japanese version of the Holy Qur'an with Arabic text was done by Umar Mita in 1972.
Mita was born as Ryoichi Mita on Dec. 19, 1892 in a Samurai (warrior) Buddhist family of Chofu town in Yamaguchi, Japan. He graduated from the Yamaguchi Commercial College in March 1916, at an advanced age of 24, because of his ill health. He visited China and learned the Chinese language. There he came in contact with Chinese Muslims and liked their way of life. He was impressed because he saw no such community life in Japan. In 1920, when he was 28 years of age, he wrote an article "lslam in China" in a Japanese magazine called "Toa Keizai Kenkyu" (Far-East Economic Research Journal). This was the first impact of Islam upon him.
Mita met Haji Omer Yamaoka, the first Japanese Muslim to perform Haj in 1909. After returning to Japan the following year, Yamaoka embarked on an extensive travel across Japanese islands introducing and explaining Islam. In 1912, Yamaoka wrote and pub1ished a number of books on his journey through Arabia and on the grand spectacles of Haj in Makkah. In 1921 Mita again met Yamaoka to learn more about Islam.
Finally, Mita embraced Islam in 1941 at the age of 49. 
At the age of 60, Mita chose to devote himself to the cause of Islam and to the learning of the Arabic language. In 1957 he went to Pakistan on invitation and undertook various journeys in connection with dawa activities. In 1958 he performed Haj. In 1960, after the sudden death of Sadiq Imaizumi, the first president of Japan Muslim Association, Mita was elected its second president. During his term as the JMA president, he wrote books including, "Understanding Islam" and "An Introduction to Islam." He also translated Maulana Muhammad Zakaria's book Hayat-e-Sahaba (Life of the Companions) in Japanese language.
Three Japanese translations of the Holy Qur'an were published in 1920, 1937 and 1950, respectively. A fourth translation from the original Arabic was published in 1957. But all these Japanese translations were rendered by non-Muslim Japanese scholars. Mita was the first Muslim to translate the Qur'an in Japanese language.
In 1968, the translation of the text was completed and its first revision was received by the Japan Muslim Association. In June 1970, Mita submitted the revised manuscript to the Muslim World League in Makkah. The manuscript was thoroughly checked by a committee of scholars and after about six months the work was finally approved for printing by Takumi Kobo Printing Company of Hiroshima.
Finally on June 10, 1972, the printing of the translation of the Holy Qur’an in Japanese was completed and its first edition was published after 12 years of strenuous efforts. It was a joyous occasion for Mita as his efforts were crowned with success at the age of 80. He died in 1976 at the age of 82. May Almighty Allah rest his soul in peace.