Taiwan was a colony of Japan for 47 years when the Pacific war began and 50 years by the end of the war. Plenty of Taiwanese people had accepted that they are Japanese subjects. Some would work especially hard to prove they are as worthy as actual Japanese. Years of imperialistic education had also convinced some that they have a duty to protect the God Emperor.
Granted most Taiwanese people were aware of the discriminatory aspects of living in Taiwan as a Taiwanese. Most schools were segregated. Workplace usually gave Japanese an unfair advantage. Many Japanese showed casual discrimination towards the Taiwanese people. The Japanese police also often tortured Taiwanese who fought for a more democratic rule. However, some Taiwanese probably still did volunteer out of their hearts because they rightfully believed they are Japanese, and were proud to be a member of the strongest nation in Asia.
That being said, the Japanese have always maintained that all kamakazis and comfort women volunteered. History has proven that as false. So just because some Japanese record said someone volunteered, you shouldn’t take it at face value.