Bleach characters move from world to world by several means. Shinigami open passages between worlds by means of their zanpakutō. Butterflies created during soul burial, called hell butterflies, make these routes safe. Human souls usually cross between planes only through birth into the human world or soul burial by shinigami. Living humans can also use special portals to move between worlds, but this is dangerous. While hollows are portrayed as able to move between planes at will by opening rifts in space, they usually remain in Hueco Mundo due to the risk of discovery in Soul Society or the human world. Encounters between characters crossing realms are a driving plot force in Bleach.
Soul Society
Soul Society: Soul Society consists of two portions: the expansive walled city of Seireitei where the shinigami and nobility reside. And the eighty-district residential area of Rukongai. Each district describes its conditions, with the lower numbered districts being more peaceful and becoming progressively harsh as the number increases. A king resides in another realm within Soul Society. Souls in the Soul Society are much like normal humans, but age at an extremely slowed rate, such that lifespans of several centuries are commonplace. Children can even be born as they are in the human world.
Soul Society is the afterlife (also called the spirit world in a Bleach-related context) in the anime and manga series Bleach. It is meant to correspond to heaven or nirvana in human belief systems.
Overview:
While Rukia Kuchiki initially describes Soul Society as something of a paradise, where nine out of ten times it is better than the living world and hunger is never a problem, Soul Society is portrayed as anything but sublime. In fact, aside from the slowed aging, life there is much like that in the living world, though Rukia's comment about no hunger is generally correct. Soul Society consists of two portions, the cities where most people live, called Rukongai; and the walled castle where the spirit world nobility and the shinigami live, known as Seireitei (lit. Court of Pure Souls).
Within Soul Society, no one is immortal, though aging is slowed to such an extent that lifespans of 2000 or more years are not unheard of. Such ages, however, are usually limited to shinigami or other Soul Society dwellers capable of manipulating spirit energy. People can also be killed as regular humans are, though it is somewhat more difficult. A soul that dies in Soul Society is reincarnated on Earth as a new human.
Accessing Soul Society:
Shinigami come and leave Soul Society by unlocking the senkaimon using a Hell Butterfly . Pluses, on the other hand, enter Soul Society through the ritual of Soul Burial.
Intruders can also pass through the senkaimon by adding a reishihenkanki (lit. spirit exchangers), which converts matter into spirit particles. However, they must first pass through dangai, the bordering dimension between the human world and Soul Society. This is much more dangerous to do, as souls that cannot pass through before the gate to Soul Society closes are trapped there forever.
Finally, hollows can also directly rip a hole to Soul Society from Hueco Mundo, or in the case of arrancar, use garganta.
Government:
Soul Society is ruled by a royal family, which is protected by a royal guard. Further down, Central 46 Chambers serves as a supreme judiciary and legislative that is second only to the royal family. The shinigami enforce order in Soul Society as a sort of executive and military branch. All of the above, except the royal family and guard, reside in the Seireitei.
The king and the royal family reside in a separate dimension in the very core of Soul Society, which can only be opened with a key, fittingly named the Royal Key. The king's practical role is unknown. The king seems to have no interest in politics and leaves the Central 46 Chambers to such affairs. According to Rangiku Matsumoto, no shinigami in the Gotei 13 has ever seen the king.
Rukongai:
Rukongai is the largest portion of Soul Society and the most populated. It is divided into 320 districts (80 in North Rukongai, 80 in West Rukongai, etc.), each numbered in descending order on how far they are from the center; this results in the higher-numerated (and farther) districts decaying into slums. Thus, while District 1 is peaceful and lawful (and in many cases resembles the antiseptic lifestyle of early-Edo era Kyoto), District 80 is a hardscrabble, violent, crime-infested area that more depicts Heian era Kyoto. There is no indication that the shinigami or any other agencies patrol the streets of Rukongai, and as a result, the citizenry are mainly responsible for their day-to-day welfare.
So far, only four names of Rukongai districts are known:
1 - Junrinan , part of West Rukongai
Tōshirō Hitsugaya, Momo Hinamori, and Jidanbō, the West Gate Keeper, came from here. When Ichigo comes to Soul Society, the spirit of Yūichi Shibata, the boy who inhabited Chad's cockatiel, also comes to reside here. According to Sōsuke Aizen, West Rukongai is also the "headquarters" of Kisuke Urahara.
78 - Inuzuri, the South Alley of Flowing Spirits
Both Rukia Kuchiki and Renji Abarai grew up here.
79 - Kusajishi, the North Alley of Loitering Spirits
Yachiru Kusajishi was found here by Kenpachi Zaraki.
80 - Zaraki, the North Alley of Loitering Spirits
Kenpachi Zaraki came from here.
Seireitei:
Seireitei is in the center of Soul Society, a circular shirō with four main entrances, each guarded by a Gate Guardian. The walls are made of deathstone, a material known to sap all spiritual and psychic energy when one portion is faced in a particular direction, similar to magnetic lodestones.
The majority of the residents of Seireitei, nobility and shinigami alike, do not interact with the citizens of Rukongai. However, residents of Rukongai are allowed to apply for the shinigami academy, which is often the only escape from the poorest conditions of Rukongai, such as Renji and Rukia. Some Seireitei residents, such as ex-shinigami Yoruichi Shihouin and the Shiba clan, do maintain residences outside
Human World
Human world: The human world of Bleach is focused on modern Japan; specifically, a fictional area of Western Tokyo called Karakura Town. In this world, Ichigo attends school and fights hollows.
Huecto Mundo
Hueco Mundo: Hueco Mundo is a dimension between the human world and Soul Society. It is where hollows reside when not hunting humans, and they are undetectable as long as they remain inside. Entrances to Hueco Mundo are created by ripping the dimensional fabric between the two worlds. On the surface of Hueco Mundo is a desert-like realm, covered in perpetual night. Few hollows reside on the surface, and the landscape is dominated by the imposing Las Noches palace. Directly underneath is the Forest of Menos, where the hollows mainly reside until provoked to leave.
Hell
Hell: Hell is the destination of those who have committed unforgivable evil acts during their lives in the human world. When a hollow whose mortal soul is too wicked to enter Soul Society is slain by a Zanpacto, the gates of hell (giant doors held by skeletons) appear and begin to open. A giant, laughing spiritual being with a blade spears the wicked spirit and drags it into hell.
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