after three years of judo training in Busan, can spoil South Korea's gold medal hopes in his division.
"I believe people in both Japan and Busan will support me," said the 21-year-old, who won the Asian championship last year as a South Korean and now fights under his legal Japanese name, Yoshihiro Akiyama.
"My pleasure should be greater than what others can feel."
He is safely separated from up-and-coming 21-year-old South Korean Ahn Dong-Jin in the 81-kilogram tournament and they may possibly clash in the final.
"I have known him since my days in South Korea. But I just take him as one of my opponents," Chu said about Ahn, who he beat last Feburary on his way to win the Paris international tournament.
Chun was born in a large Korean community in Japan's second city of Osaka and started judo at the age of three under the guidance of his father, who himself was a competitor in the martial art which Japan gave to the world.
He moved to this bustling South Korean port city after college because he knew he would not be allowed to join corporate-sponsored Japanese judo clubs as far as he remained South Korean.
As a member of the judo team at the Busan Municipal Office, Chu beat Sydney Olympic silver medallist Jo In-Chul at the Korean Open in late 2000. He won his first major title at the Asian championships in February last year.
But his track record was not enough to convince South Korean judo chiefs. Jo was the one who was selected for the world championships in Munich last year where he glittered with gold.
The disappointment prompted Chu, who had been growing increasingly disenchanted with South Korea's spartan training methods, to return to Japan.
"I learned a lot in different aspects and saw a kind of professionalism grow inside me," said Chu.
"I didn't think too much about whether I was Japanese or Korean. It is as natural as changing clothes," he talked about his switch of allegiance.
As Akiyama, he has lifted the prestigious Kodokan Cup as well as the international tournaments in Japan and France this year.
"I am sure Korean officials will come to see how strong I have become," said Chu, who dyes his hair blond. "I want to stand out in a way to make them feel jealous."