We learn a bit more about this mysterious warrior's background as the story progresses.
Although his father was Chinese, he grew up in Japan. We don't know if his mother was Japanese or Chinese. The father of the Japanese warrior was a very intelligent man, a Jack of all trades, master of none. He learnt many different things in his life, including martial arts. But he never reached the highest level in any of those things, he wanted to become a renowned martial arts expert. But was constantly defeated by the true masters of martial arts. In the end he felt depressed and angry and took his baby son and left for Japan.

He wanted his son to become the master of martial arts he couldn't be. As soon as his son could walk he taught him the ways of the sword. He bathed the young son in herbal medicinal baths to strenghten his bones and tendons.
Although this man wasn't a very good martial artist himself, he proved to be an excellent teacher. At the age of 11, 12 the Japanese warrior was already equal to the first rate martial artists of Japan. Although Japanese warriors often duelled to the death, they felt there was no honour in killing a mere boy. So he learnt from his defeats and his experience in combat grew.

At the age of 18, 19 he was one of the elites of the Japanese Wulin and was said to be even invincibile in Japan. His martial arts was the accumulation of the essences of both the great Chinese martial arts schools and Japanese martial arts schools.
The three leading Wulin elders of Japan had fought him several times in these years and every time their respect for the Japanese warrior grew. According to them, the warrior's martial arts were magnificent.

Around this time his father had passed away, but he seemed to be unmoved by it. He continued his training, not only was his body seemingly made of steel it would seem that his heart was of steel too.
At the age of twenty he knew that he was undefeated in Japan and knew that if he stayed here his martial arts would never progress any further. So, he left for a desolate isle near Japan. On that isle there were numerous small white and black stones, resembling go pieces. So, the local people called that the Isle of Go. He lived on that desolate and harsh isle for ten years, he spent his time contemplating and studying go. It seemed that he lost interest in martial arts.
But when he left the isle and returned to Japan, his martial arts were raised several levels higher. According to the three leading Japanese elders, before he left for the isle, his martial arts level was still comprehensible but now it was deep and seemingly boundless.

He challenged one of the elders to a duel. Both of them just stood there neither of them moved. They stood there for 14 hours, untill the Japanese elder couldn't stand it anymore and passed out he succumbed to the awesome power of this Japanese warrior. The willpower, martial arts and the sword of the Japanese warrior became one entity, one great awesome, omnipotent power.
He felt confident now to go to China to do what his father couldn't.
He killed several of the top leading martial arts experts of China with one slash between the eyebrows. He shocked the entire realm.
The top ten elite martial arts experts gathered at the Linking Cloud Manor to challenge him. One by one, those experts died. One stance was enough. When someone threatened him by saying:"There are hundreds of us, if all of us attacked at once. You wouldn't be able to withstand such an assault."
the Japanese warrior was unfazed and coldly responded:"Warriors should die in battle, if I was killed by the sword or sabre I am merely fulfilling my destiny." Everyone felt ashamed.

The number one martial artist in China, the Purple Marquis learnt of the Japanese warrior and issued a challenge. The Purple Marquis uses his sword to pierce/seal seven acupoints of a man in one stance and told people to bring that man to the Japanese warrior. Upon seeing that man and those sword "wounds" the Japanese warrior realised that he had found a true adversary.

So, he asked where the Purple Marquis was and could not be bothered by the remaining suriving four of the ten top martial arts experts.
His words were:"The way of the martial arts is like climbing a mountain, now that I have found the highest peak. The lesser mounts are of no importance."
And he left for the beach of the Eastern Sea.

The Purple Marquis and the Japanese warrior duelled on sea, both were on two small rafts. After an intense battle, the Purple Marquis won by half a stance. However, the omnipotent internal energy of the Japanese warrior had mortally injured the Purple Marquis. the Japanese warrior being a true master admitted defeat to the Purple Marquis and said he would return seven years later for a rematch. The Purple Marquis died the following night.

The Japanese Wulin was shocked to hear that the Japanese warrior had lost and feared that the defeat would have driven him insane. No one in Japan is his match, and if he would go mad that would mean doom for everyone. So the three elders of Japanese Wulin assembled a group of top martial arts experts to contain/kill him if necessary. All means would be allowed, although they commented that such an action would be honourless, but the Japanese warrior was a product of the Japanese Wulin so they have a responsibility to stop him.

However, the Japanese warrior didn't go mad. Before his journey to China he was cold man that never smiled. But now, he was friendly and even started a small busniness on the market. And whenever someone would ask about the rematch seven years later, he would just smile and shake his head.
Everyone thought he had forsaken the path of the warrior untill one year of the rematch. He had disappeared.
And suddenly the Wulin of China received a letter from him:

My respects to whom this may concern,

The death of the Purple Marquis has greatly saddened me. With his death, I am lonelier than before. I know now that victory does not come easy, but finding defeat is even more difficult.
But the match that was set seven years ago will still continue, next year I will be on the beaches of the Eastern Sea again. I sincerely hope that someone with a sword will be able to grant me a defeat.

The warrior of the Eastern Sea.