Interesting article, JC.
There's been several stories about Koreans under the Japanese military here in the Philippines. All that I heard from my elders is anecdotal and try as a might, I haven't really unearthed any documentation about this.
However, there is a common thread in all there recollections.
They claim that many Koreans drafted into the Japanese Army were usually more brutal to Filipinos than the Japanese themselves. My elders explain that this was so because since the Koreans were brutalized by the Japanese and that Filipinos were the convenient outlet for some emotional release by these individual Koreans. Take note, I say individual Koreans because this is not to meant to be racist against Koreans as a whole. I have several Korean friends but somehow, I feel that raising this issue with them is not appropriate. Maybe by putting this here, I may be able to learn a thing or two about this.