Kotaku (こたく), more commonly known as Shinsenkyō (神仙郷, Literally meaning: Divine Paradise), is an island located within the southwest seas that is far beyond the Ryukyu Kingdom and is inhabited by monsters. The island had been said to possess the legendary Elixir of Life, which had been sought out by humans for centuries. Kotaku is the main setting throughout the series.
1,000 years ago, Xu Fu made landfall on the island after his quest to retrieve the legendary Elixir of Life for Emperor Qin Shi Huang came to an end. He then declared himself ruler and decided to devote his life in researching the secrets to immortality by experimenting with Tao, resulting in the creations of abnormal creatures. The people that accompanied Xu Fu were also converted into a race known as the Hōko where their lives became extended through an unknown experimental process.
Upon Xu Fu's passing due to the condition known as Arborification, Xu Fu's wife, Rien, made a commitment to revive her husband by completing Xu Fu's research in developing an Elixir of Life with the help of seven lifeforms she created with her own Tao. Together they became the new rulers of Kotaku known as Lord Tensen. While devoting themselves to the ways of Tao in Hōrai, the group guided the Hōko through the Sōshin using fabricated beliefs involving mortality in order to secretly observe their way of life, as well as use them as resources to replenish their lost Tao in the midst of their training. Mei, one of the members of Lord Tensen, caught wind of Rien sacrificing the lives of the Hōko for her research and tried to stop her. Rien then punished her for this defiance and made her whereabouts unknown to the other Tensens.
After 200 years passed, the Hōko began to go on the verge of extinction from undergoing Arborification. This caused the members of Lord Tensen to become concern, due their worries about losing their source of nourishment, and came up with the idea of luring in humans from the mainland to act as replacements. Eventually, their plan became successfully as they managed to ambush the first group of humans who came to the island and discovered how valuable the human race's Tao was. They then managed to create the prototype elixir known as Tan from the humans they captured and would be supplied with endless amounts of Tao. The humans who came to the island were also forcibly converted into loyal servants of Lord Tensen and were taught in the ways of Tao.
At some point, the humans of the mainland became convinced that Kotaku was the legendary land known as Shinsenkyō where it was rumored to be where the Sennin reside and where the legendary Elixir of Life is held. Because of this rumor, many humans throughout the ages journeyed off to the island in hopes to retrieve the elixir, only to fall to either the island's monsters or by Lord Tensen.
During the Edo period, after believing that the Elixir of Life resided on Kotaku, the shogun sent out at least six expedition teams to Kotaku to investigate. With each team, only a single boat filled with flowers and a bloomed human made it back to Japan (as per Lord Tensen's plan to lure in more humans). This increased the shogun's curiosity and decided to send a group of death-row criminals and assigned executioners to the island for the next expedition team. Kotaku then received visiting humans that would cause the island to go into disarray after the remaining survivors managed to get pass the monsters, reach Hōrai where the Sennin reside, and defeat three Dōshi and one member of Lord Tensen. However, after meeting Aza Chōbei, one of the surviving humans who achieved hybridization with the Tao of the Waitanhua Flower, and performed experimentations on him, Rien managed to create the perfected Tan elixir and was ready to depart to Japan to create more using the lives of the countries populace, which would complete her plan of reviving Xu Fu. Upon Hōrai being invaded by the surviving humans, Ran, Ju Fa, and Tao Fa of Lord Tensen met their end while Zhu Jin received major damaged to their body. Chaos soon broke out after another group of strong humans arrived shortly and Zhu Jin deciding to assimilate themselves with the Banko. After procuring a ship, the surviving humans manage to sail away from the island, making them the first group of humans to have escaped Kotaku alive, while Gui Fa, the last remaining Tensen alive, also makes their leave as well with the Basin containing the plant ovules of the deceased Tensens. The island is presumed to have died off after Gui Fa had noted that the destruction of the Banko's Tao caused the Tao of the island to be destroyed as well, which was a sign that Kotaku would soon wither away.
Kotaku derives from two religions: Taoism and Buddhism. The man-made statues on the island combines these two religions (though Senta found them to be poorly executed). The inhabitants also wear clothing that associated with these religions.
Flora and Fauna
The island's animal life consists of the experimental creatures created by Xu Fu, such as the human-faced insects, Sōshin, and Mōnshin. The creatures' main instinct is to attack any foreign trespassers. The Sōshin were also in charge of guiding the Hōko as per Lord Tensen's orders. The Wadatsumi are the only water-based animals on the island and would attack anything trying to escape Kotaku if it has not come from Hōrai's floodgates.
After Kotaku was discovered by humans, the island's forest became bundled with bloomed samurai who were presumably victimized by the Paradise Butterflies carrying mature samples of Tan, resulting in them undergoing Arborification. According to Gabimaru's expedition of the island, most of the plant life were familiar types that could be found on the mainland but also had a few flowers that were unfamiliar. To some, this gave the island a fairy tale-like feel the moment one steps on land, while others may feel the exact opposite, thinking that the mixture of plant life is unnatural and artificial. One flower in particular that is most common on Kotaku is the Waitanhua Flower, a flower designed by Lord Tensen to convert humans into Tan and was found within the Tan pit. A large Waitanhua Flower known as the Banko was kept in Hōrai.
1,000 years ago, Kotaku used to have wildlife, such as deer and birds. They soon died off after a century had passed.
Kotaku is divided into three regions: Eishū, Hōjō, and Hōrai.
Eishū (えいしゅう) is the outer region of the island, which holds the forest and the beach. The forest is covered in plant life, mainly due to the blooming corpses of samurai that last ventured the island. The Sōshin are stationed in Eishu to eliminate any trespassers.
- Further information: Hōjō
Hōjō (ほうじょう) is the second region of the island. Hōjo is a valley that circles around Hōrai and where the Sōshin nest. The Hōko once resided in Hōjō in a small village 1000 years ago until they underwent Arborification, leaving the village in ruins. Years later, Hōko and Mei became the only known people residing in the village.
- Further information: Hōrai
|Rien †||Xu Fu †|
|Gui Fa||Ju Fa †||Mu Dan †||Ran †||Tao Fa †|
|Zhu Jin †|
|Butterfly Dōshi †||Centipede Dōshi †||Lettuce Dōshi *||Tentacle Dōshi|
- The three regions of Kotaku are based off of three of the five islands the Eight Immortals resided, as well as the islands Xu Fu tried to locate on his voyage.
- In Senta's opinion, because Kotaku takes religions from the outside world, the island could not be viewed as Shinsenkyō.
- Officially, only thirteen humans in history have managed to survive and escape Kotaku.
- Out of the thirteen, Yamada Asaemon Jikka is the only human to have successfully escaped the island twice.
- According to Shugen, the distance from Eishū to Hōrai is about 8 ri (31 kilometers), which takes at least two hours to arrive when traveling on foot.
- After reflecting on the journey, Jikka compared the island to Onigashima (literally "island of oni/ogres") in the Japanese folktale of Momotarō. Ironically, the original story idea for Jigokuraku was suppose to be an expedition to Onigashima to eliminate the demons living on the island.
- According to the Q&A of Jigokuraku Kaitai Shinsho, the outline of Kotaku is based off of the science fiction novel, The Island of Doctor Moreau, which is confirmed to be Kaku's favorite novel. The novel also acted as the "skeleton" to the whole story of Jigokuraku.