Was there a book about the protagonist who traveled through the world of One Piece and was called Kuzan?

The protagonist transmigrated to the world of One Piece, a novel called Cousin.

Answer 1

It might not be exactly what you want, but I would recommend a novel that is most relevant to your description."One Piece's Journey to Ten Thousand Worlds" is a light novel by the oldest author, Gu Gu. It is a derivative doujinshi novel. The general plot of this novel is as follows:

At the beginning, he passed through One Piece.
This was the story of the Pirate King who began to roam the myriad worlds and roam the heavens.
[Current status: One Piece (Hot Series)-To be determined-]
[PS: The introduction is too weak, please move to the main text!]
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"One Piece Revolution" was a light novel written by the author who chanted scriptures and sang. It was a derivative doujinshi novel. The general plot of this novel was:

After watching One Piece's finale, he traveled back to the era of the great pirates, and with the profound meaning of ninjutsu, what kind of gorgeous collision would happen between pirates and ninjas?
When Krogdal encountered the Sand Escape, when Ainilu encountered the Thunder Escape, when Ace encountered the Fire Escape, when the Six Navy Styles encountered the Eight Gates Escape, when all aptitude users encountered the Water Escape...
Let's see how the defected prince steps on the road of revenge, using the dark forces of the underground to overthrow the world government and set off a worldwide revolution.
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One Piece: The Navy's Dominating Fist was a light novel by the author, Secret Collection of the Starry Sky. The general plot of the novel was:

Traversing the world of pirates, becoming a navy marshal step by step, leading the navy to break away from the world government and establish a new world government.
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One Piece's Manipulation of the World was a light novel written by the author, the 11th generation. The general plot of the novel was:

After so many years, I've come to write another book,"Creating Justice and Order in the World of Pirates".
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One Piece: Dominate the World was a light novel by the author, Banishing Smile. The general plot of the novel was:

Never underestimate the evil thoughts that a person could have, especially in a world where martial arts was paramount.
Desire was endless. Power, reputation, wasn't this everything that pirates pursued?
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One Piece: Seat of the Void was a light novel written by the author, the 11th. The general plot of the novel was:

New book, Creating Justice and Order in the World of Pirates.
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"One Piece: The Strongest Sea King" was a light novel written by the author, Dream Shelter No. 2. The general plot of this novel was:

Xia Qiu transmigrated to One Piece's world and became a fish.
He continued to devour and began a path of evolution.
Fish, Sea Beasts, Sea Kings, Large Sea Kings, Super Large Sea Kings.
He devoured pirates and warships, fought against the Seven Martial Seas, liberated Fishmen Island, fought against the Four Emperors, attacked Marin Fudo, and attacked the World Government.
As time passed, he became the nightmare of all pirates. His image lingered in everyone's hearts and gradually became a legend.
Who said that Sea Kings couldn't become the strongest in the world?
I'm the man who wants to become the Sea King.
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One Piece: The Bandit Commander was a light novel by the author, Liu Xianggu. It was a derivative doujinshi novel. The general plot of the novel was as follows:

Yun Fei, who had traveled through the world of pirates, had stolen a mysterious demonic fruit from the hands of a Heavenly Dragon. He did not expect to obtain the greatest potential, an ability that was large enough to change the world. From then on, Yun Fei embarked on a path that pushed all the experts aside and constantly became stronger. But at the same time, he was also caught in the whirlpool of the world's greatest secret! The path was made by people. If there was no way out, then I would kill my way out! This was a pure One Piece Doujinshi novel. The plot was slow and step-by-step, and the later it was, the more exciting it became. The world structure and power system never deviated from the original! Don't spray if you don't like it!
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One Piece: All the Villains was a light novel by the author, Little Hymie. The general plot of the novel was:

McCann, who had transmigrated to the world of One Piece, obtained the Golden Finger Pirate Ship that summoned the villains of all worlds, the Black Pearl; the vice-captain and voyager, Héctor Barbosa; the ship's cook, Hannibal Lecter; his personal assistant, Harry Quinn; and the boatman, Jigsaw. Moriarty, the archaeologist; Nanase, the head boatswain; Jason, the captain's guard; Fran, the ship's doctor; and all in all, it was a party for the villains.
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One Piece: The Food Hunter of Qinghai was a light novel written by the author who lived in Duwangting. The general plot of the novel was:

[One Piece]+[Captive of Food] Doujin was a story of a poor child who was tricked by his grandfather on Food Earth and transmigrated to the world of One Piece.