 when the Korean Peninsula was under Japan's colonial rule. Jeju Island is now part of South Korea.
Ko Tae Mun came to Japan when he was 13 to join his father.
An elderly resident of Tsuruhashi said a famous black market in the district in the immediate aftermath of World War II was controlled by Korean nationals.
"Many of those individuals walked around as if they owned the place. The Japanese seemed to take a step back. (Ko), who would use a nearby bathhouse, always walked around with a proud bearing."
Ko learned judo from a Japanese while living in Osaka.
The resident recalled: "Ko's wife did sewing at home. Many of the Koreans living here came from Jeju. His wife was a hard worker, but her husband was always drinking and doing as he pleased. There were many households like that."
Ko often visited a dojo that was on the first floor of a building that housed a newspaper for a Korean organization on the second floor.
A Korean national in his 80s who worked at the newspaper said: "Four Korean nationals often gathered at the first floor judo hall to teach judo. It was said that when all four were around, they had nothing to be afraid of."
One of those individuals was Ko.
The division in the Korean Peninsula led to the creation of South Korea and North Korea in 1948.
Perhaps because he was having difficulties making a living solely from judo, Ko in 1956 started his own professional wrestling group with ethnic Korean businessmen serving as sponsors.
That was the era in which Rikidozan, himself a Korean national, sparked a wrestling boom in Japan, then desperate for local heroes after its defeat in war, by staging bouts in which Japanese usually defeated their much larger American opponents.
Rikidozan concealed his Korean roots and became very wealthy as well as a hero to the Japanese. Ko wrestled under the name of Daidosan after the river that flows through Pyongyang.
However, his wrestling group never took off, and Ko disbanded it soon after.
In 1961, the family boarded a ship in Niigata bound for North Korea under a program begun in December 1959 by Kim Il Sung to repatriate Korean nationals living in Japan.
The move to North Korea was for more than simply economic reasons.
As part of a plan to host an international sports event for newly developing nations, Kim Il Sung wanted to create a judo association in North Korea. As far as he was concerned, the man for the job was Ko.
A former high-ranking official of the Pyongyang-affiliated General Association of Korean Residents in Japan (Chongryon) said, "(Two officials) of a sports association affiliated with Chongryon in Osaka were given instructions, and they approached Ko and asked him to return to North Korea."
Although Ko was only a minor pro wrestler in Japan, his move to North Korea would eventually lead to him being referred to as the father of North Korean judo.
Another Korean national who also moved to North Korea learned judo from Ko and would later flee the North for South Korea.
The individual once said, "Those who built the foundation of North Korean judo were all Korean nationals who moved from Japan. Ko's daughter, Young Hee, resembled her mother and was slim and very pretty. She would often visit the judo hall."
Having become the daughter of an influential figure in North Korean judo, Young Hee in around 1970 joined the Mansudae Art Troupe as a dancer.
It was there that she caught the roving eye of Kim Jong Il. While Korean nationals who returned to North Korea from Japan were often discriminated against, Young Hee experienced a Cinderella story of sorts.
In 1973, she came to Japan as the lead dancer of the Mansudae Art Troupe.
Ko Young Hee performing with the Mansudae Art Troupe
An individual with ties to Korean nationals said, "Her visit to Japan was a present from Kim Jong Il. He basically told her to go to the Japan of her birth and buy whatever she wanted. She was treated very specially and those around her were very nervous about not upsetting her."
Ko Tae Mun died in Pyongyang in 1980. Ko Young Hee gave birth to three children. She died of cancer in 20