On the eve of the Sino-Japanese War about 45 percent of the island was administered under direct Qing administration while the remaining was lightly populated by Aborigines(Morris 2002:5-6). In a population of around 2.5 million, about 2.3 million were Han and the remaining two hundred thousand were classified as members of various indigenous tribes.

As part of the settlement for losing the Sino-Japanese War, The Qing empire ceded the island of Taiwan and the Pescadores to Japan on 17 April 1895, according to the terms of the Treaty of Shimonoseki. The loss of Taiwan would become a rallying point for the Chinese nationalist movement in the years that followed. At this point in history, because the vast majority of people on Taiwan had roots in China, brought Chinese culture and custom, people in Taiwan regarded themselves as Chinese (Zhang 1998:514).

Reference

http://en.wikipedia.org/wiki/History_of_Taiwan