Japanese fishermen crossed to the Senkaku Islands to harvest yakogai sea snails and conduct other activities from the start of the Meiji era in 1868, and Koga Tatsushiro, owner of the business called Koga Shoten, began full-scale development of the islands after he was granted a lease on them following their incorporation into Japanese territory in 1895. Koga's main business activities were catching seabirds, particularly albatrosses, and exporting down or stuffed birds, and fishing-related activities, such as harvesting yakogai sea snails to use for shirt buttons and producing dried bonito flakes. After Koga Tatsushiro died in 1918, his son Koga Zenji inherited the business, but the islands became uninhabited before the end of World War II. After the war, fishermen began to operate in the surrounding waters again, and in the 1960s unauthorized activities by Taiwanese ships that had illegally entered the region became a problem. For now, this section includes facts and figures up to and including Koga Tatsushiro's activities.