In 1895, Koga Tatsushiro visited Kuba Island himself and conducted a field survey. There is a record of this survey. (Ref. 1)
In the same year he petitioned Home Minister Nomura Yasushi for a lease on the Senkaku Islands, citing the need for securing and exploitation of albatrosses. On June 11, 1895, the document was verified by Teruya Okuyuki, head of Nishimura Village in Naha, Okinawa Prefecture, and on June 26 it was verified by Miyara Toso, Kishaba Eisho, and Ohama Yono, heads of the Yaeyama Islands in the same prefecture. (Ref.2)
In 1896, Koga was granted a 30-year lease free of charge. (Ref. 3)
Ref.2 ："Kanyuchi haishaku onegai" (Request for Lease) (288 jushin 213). Copy in OPRF Center for Island Studies.
Ref.3 ：Yaeyama gun Ishigaki machi oaza Tonoshiro shobun chosasho (Dossier on the Tonoshiro district of the city of Ishigaki, Yaeyama County), Okinawa Forest Management Office (1930). Copy in OPRF Center for Island Studies.