DC,
There is truth to Koreans serving in the Japanese military during WWII:
"From Korea, 116 thousand soldiers and a further 120 thousand auxiliaries served the imperial military.  From Taiwan, 80 thousand soldiers and 126 thousand auxiliaries. 　These auxiliaries have joined the military and served mainly in non combat roles such as prison guards."  Found at:  https://www.quora.com/What-units-of-the-Imperial-Japanese-Army-in-WWII-were-mainly-made-up-of-Korean-and-Taiwanese-recruits-and-where-did-they-fight

I spent all of about 15 seconds finding that.  Now for the hard part, verifying the veracity of the information, identifying nuances, and putting it all into context to determine "truth".