During his long life in China, he saw Islam firsthand and developed an interest in it, becoming a preeminent consultant to Japanese forces on Islam-related questions after he had been hired as a propagandist, although it wasn't until 1941 that he formally converted.
Throughout this period, Mita was known to have met and had close discussions with Shūmei Ōkawa, another translator of the Quran and fellow pan-Asianist.
Mita engaged in spy work for the Imperial Japanese Army and wrote of the need to propagandise Muslims in China in order to obtain their support against the Han Chinese forces.
[3] After the end of World War II, Mita focused his efforts solely on Islam.
He joined the recently-founded Association of Japanese Muslims (日本ムスリム協会) in 1952, becoming its leader from 1960 to 1962, whereafter Mita left for Pakistan and Saudi Arabia so as to learn Arabic and translate the Quran into his native tongue, a task that he would complete a decade later in 1972.