Rokudo is a Buddhist term and it means six posthumous worlds to which the souls of the dead transmigrate. The six worlds that constitute Rokudo are as follows.
Jigoku-do (world of hells)
Gaki-do (world of hungry ghosts)
Chikusho-do (world of animals)
Shura-do (world of bellicose demons)
Ningen-do (world of humans)
Ten-do (world of heavenly beings) (also called Tenjo-do or Tenkai-do)
According to Buddhism, it is believed that stray lives that came in to the world will transmigrate after death to one of six posthumous world depending on the crimes they committed while alive and repeat life and death in each of the Rokudo where they transmigrated (Rokudo-rinne, Rebirth in the Six Worlds). Even those transmigrated to Ten-do cannot escape from the rebirth of pain. Based on the principle that all things are in flux and nothing is permanent, it is believed that lives are destined to die out eventually and transmigrate to another world (or the same world) regardless of the world to which they transmigrated. Under the world view of Shumisen (Mt. Sumeru), the six worlds mentioned above are sometimes understood as space.
Those lives that deviated from the road of the wheel of life, such as Tengu (braggart), are commonly called Gedo (Maen).
In the picture depicting the wheel of life, such as the one shown in upper right,
monster and skeleton represent ignorance (Mumyo) and uncertainty regarding the root of the Twelve-fold Chain of Dependent Origination,
the outer circular ring represents human behavior (omen),
the second circular ring represents Rokudo (in this picture, heavenly beings, human beings and Ashura occupy the same place),
the inner circular ring represents human beings, and
the circle in the middle represents wrath (symbolized by snakes) that is the cause of pain, folly (pigs) that represents ignorance and greed (birds)
In connection with Rokudo, the belief of afterlife that souls are saved from the world to which they transmigrated by the guidance of Kannon (Deity of Mercy), called Kannon belief, was generated and it was believed that six different Kannon bear respective roles. These are called Roku Kannon (the six Kannon). Tendai sect and Shingon sect adopt different interpretations concerning Ningen-do and Fukukensaku Kannon (Kannon of the Never Empty Lasso) and Jundei Kannon (Cundi) are adopted, respectively. When called Shichi Kannon (the seven Kannon), these two Kannon are included.
Roku Kannon in Shingon sect
Roku Kannon in Tendai sect
Jigoku-do; Sho-Kannon (Sacred Kannon, or Aryavalokitesvara); Sho Kannon
Gaki-do; Senju Kannon (Thousand Armed Kannon, or Thousand Armed Avalokiteshwara); Senju Kannon
Chikusho-do; Bato Kannon (horse-headed Kannon); Bato Kannon
Shura-do; Juichimen Kannon (Eleven-faced Kannon); Juichimen Kannon
Ningen-do; Jundei Kannon; Fukukensaku Kannon
Ten-do; Nyoirin Kannon (the Bodhisattva of Compassion); Nyoirin Kannon
Difference concerning the view on life and death
Nirvana, which means awakening to Buddha through Satori (enlightenment), can be achieved while in life, and is not necessarily triggered simply by death. Nirvana is a fundamentally different notion from the phenomenon of posthumous transmigration and as represented by Shaka, human beings can live in the same world as before until their death even after awakening to Buddha since no special world is prepared for Buddha. Compared with Rokudo, nirvana can be understood as a more psychological notion.
Historically, the pure land philosophy that is held by Jodo-kyo etc. was established long after the establishment of Rokudo-rinne philosophy. The pure land is common with Rokudo in the sense of a place where the dead are destined to go, but it is a completely different notion from the world-view under the philosophy of Rokudo-rinne. The pure land can be defined as the world where Buddha resides and is not limited to one of the Rokudo.
List of Rokudo
Ten-do is the world where Tenjin (heavenly beings) reside. Tenjin are believed to have very long life-spans and be better and far less pain than human beings. Tenjin are also believed to be able to fly in the sky and spend a life of pleasure. But Tenjin are not relieved from Bonno (earthly desires). When Tenjin are dying, it is believed that five changes occur. These changes are called Gosui (Tenjin Gosui) and when such changes occur, they stink with their body being covered in grime, they sweat from the underarms, they become less fond of the place where they reside and flowers on their heads wither.
Literally, Ningen-do is the world where Ningen (human beings) reside. Although it is a world with so much pain, it is believed that pleasure may come after a succession of pain. There is also relief that those can become a Buddha.
Shura-do is the world where Shura reside. Shura are believed to fight and struggle all the time. Although it is a world where pain and anger are constantly rampant, it is not a hellish place and pain can be largely attributed to oneself in this world.
Chikusho-do is the world where oxen and horses reside. As oxen and horses live almost solely with instinct and are forced to work by human beings, they are unable to attain Buddha's teaching by themselves and in this sense, this world is believed to be of less relief.
Gaki-do is the world where Gaki (preta) reside. Gaki have the appearance of a demon with a bloated belly and they always suffer from hunger and thirst because food becomes ash when they are set to eat. There is an example of a person who was thrown into this world because he didn't care for other people while in life.. Segaki-e (hungry ghosts' feeding rites) is held on July 15 of lunar calendar in order to save these Gaki.
Jigoku-do is the world for making human beings atone for crimes committed during their life. Refer to Jigoku (Buddhism) for details.
Concerning the above six worlds, Jigoku, Gaki and Chikusho are sometimes collectively called San-akushu (literally, three bad realms, San-akudo, Sanaku or Sanzu) and Shura, Ningen and Ten are collectively called San-zenshu (literally, three good realms). Jigoku, Gaki, Chikusho and Shura are sometimes collectively called Shi-akushu (literally, four good realms).
Further, Rokudo other than Shura are sometimes collectively called Goshu (literally, five realms). Under early Buddhism, Jigoku, Gaki, Chikusho, Ningen and Ten were collectively called Goshu and Shura did not exist. Therefore, Goshu is deemed as an older notion than Rokudo. Originally, Shura (Ashura) was included in Tenbu (Deities who reside in a heavenly realm, one of six realms in which the souls of living beings transmigrate from one to another) but after Mahayana Buddhism was established, Shura derived from Tenbu and became Rokudo. Therefore, these two notions are collectively called Five Realms Six Paths.
Rokudo originated from ancient Indian philosophy before the establishment of Buddhism and did not have a significant meaning in early Buddhism. It is perceived that systematization proceeded at a later stage in history.
Although not originating from India or China, Roku Jizo (six Jizo Bodhisattva) which are allocated in each Rokudo, were enshrined throughout Japan in the 11th century and widely worshipped by ordinary people.