Imperial House of Japan in the context of "Northern Court"

The emperor of Japan is the hereditary monarch and head of state of Japan. The emperor is defined by the Constitution of Japan as the symbol of the Japanese state and the unity of the Japanese people, his position deriving from "the will of the people with whom resides sovereign power". The Imperial Household Law governs the line of imperial succession. Pursuant to his constitutional role as a national symbol, and in accordance with rulings by the Supreme Court of Japan, the emperor is personally immune from prosecution. By virtue of his position as the head of the Imperial House, the emperor is also recognized as the head of the Shinto religion, which holds him to be the direct descendant of the sun goddess Amaterasu. According to tradition, the office of emperor was created in the 7th century BC, but the first historically verifiable emperors appear around the 5th or 6th centuries AD.

The role of the emperor of Japan has historically alternated between a largely ceremonial symbolic role and that of an actual imperial ruler. Since the establishment of the first shogunate in 1192, the emperors of Japan have rarely taken on a role as supreme battlefield commander, unlike many Western monarchs. Japanese emperors have nearly always been controlled by external political forces, to varying degrees. Between 1192 and 1867, the shōguns, or their shikken regents in Kamakura (1203–1333), were the de facto rulers of Japan, although they were nominally appointed by the emperor. After the Meiji Restoration in 1868, the emperor was the embodiment of all sovereign power in the realm, as enshrined in the Meiji Constitution of 1889. Since the enactment of the 1947 constitution, the role of emperor has been relegated to that of a ceremonial head of state without even nominal political powers. The emperor is the head of the Japanese honors system, conferring orders, decorations, medals, and awards in the name of the state and on behalf of its people in accordance with the advice of the Cabinet.

The Imperial Palace (皇居, Kōkyo; lit. 'Imperial Residence') is the main residence of the emperor of Japan. It is a large park-like area located in the Chiyoda district of the Chiyoda ward of Tokyo and contains several buildings including the Fukiage Palace (吹上御所, Fukiage gosho) where the emperor has his living quarters, the main palace (宮殿, Kyūden) where various ceremonies and receptions take place, some residences of the Imperial Family, an archive, museums and administrative offices.

The 1.15-square-kilometer (0.44 sq mi) palace grounds and gardens are built on the site of the old Edo Castle.

The Meiji Restoration (明治維新, Meiji Ishin; Japanese pronunciation: [mei.(d)ʑi iꜜ.ɕiɴ, meː-]), referred to at the time as the Honorable Restoration (御維新／御一新, Goi(s)shin), also known as the Meiji Renovation, Revolution, Regeneration, Reform, or Renewal, was a political event that restored imperial rule to Japan in 1868 under Emperor Meiji. Although there were ruling emperors before the Meiji Restoration, the events restored practical power to, and consolidated the political system under, the Emperor of Japan. The Restoration led to enormous changes in Japan's political and social structure and spanned both the late Edo period (often called the Bakumatsu) and the beginning of the Meiji era, during which time Japan rapidly industrialised and adopted Western ideas, production methods and technology.

The origins of the Restoration lay in economic and political difficulties faced by the Tokugawa shogunate. These problems were compounded by the encroachment of foreign powers in the region which challenged the Tokugawa policy of sakoku, specifically the arrival of the Perry Expedition under orders from United States president Millard Fillmore. Under subsequent unequal treaties, Japan was forced to open to the West, questioning the shōgun's political authority over maintaining Japanese sovereignty. The Emperor's rebuke of shogunal actions led to the emergence of an ideological divide within the samurai class concerned with their feudal obligations to both the shōgun and the Emperor. Many lower and middle-ranking samurai became shishi ("men of spirit") who were committed to the Emperor's proclamations to expel the barbarians. Factional disputes within the domains led some domains to conflict with the Tokugawa. After some initial setbacks, the domains organised into an anti-Tokugawa alliance, and, led by Satsuma and Chōshū, they overthrew the shogunal system.

Tochigi Prefecture (栃木県, Tochigi-ken) is a landlocked prefecture of Japan located in the Kantō region of Honshu. Tochigi Prefecture has a population of 1,897,649 (1 June 2023) and has a geographic area of 6,408 km (2,474 sq mi). Tochigi Prefecture borders Fukushima Prefecture to the north, Gunma Prefecture to the west, Saitama Prefecture to the south, and Ibaraki Prefecture to the southeast.

Utsunomiya is the capital and largest city of Tochigi Prefecture, with other major cities including Oyama, Tochigi, and Ashikaga. Tochigi Prefecture is one of only eight landlocked prefectures and its mountainous northern region is a popular tourist region in Japan. The Nasu area is known for its onsens, local sake, and ski resorts, the villa of the Imperial Family, and the Nasushiobara station of the Shinkansen railway line. The city of Nikkō, with its ancient Shintō shrines and Buddhist temples, is a UNESCO World Heritage Site.

The Imperial Household Law of 1947 (皇室典範, Kōshitsu Tenpan) is a Japanese law that governs the line of imperial succession, the membership of the imperial family, and several other matters pertaining to the administration of the Imperial Household.

In 2017, the National Diet changed the law to enable the Emperor Akihito to abdicate within three years. With this change, he abdicated on 30 April 2019 and was succeeded by his eldest son, Naruhito on 1 May 2019.

Amaterasu Ōmikami (天照大（御）神; Japanese pronunciation: [aꜜ.ma.te.ɾa.sɯ | oː.mʲiꜜ.ka.mʲi]), often called Amaterasu ([aꜜ.ma.te.ɾa.sɯ]) for short, also known as Amateru Kami (天照神) and Ōhirume no Muchi (大日孁貴), is the goddess of the sun in Japanese mythology. Often considered the chief deity (kami) of the Shinto pantheon, she is also portrayed in Japan's earliest literary texts, the Kojiki (c. 712 CE) and the Nihon Shoki (720 CE), as the ruler (or one of the rulers) of the heavenly realm Takamagahara and as the mythical ancestress of the Imperial House of Japan via her grandson Ninigi. Along with two of her siblings (the moon deity Tsukuyomi and the impetuous storm-god Susanoo) she ranks as one of the "Three Precious Children" (三貴子, mihashira no uzu no miko / sankishi), the three most important offspring of the creator god Izanagi.

Amaterasu's chief place of worship, the Grand Shrine of Ise in Ise, Mie Prefecture, is one of Shinto's holiest sites and a major pilgrimage center and tourist spot. As with other Shinto kami, she is also enshrined in a number of Shinto shrines throughout Japan.

The first human inhabitants of the Japanese archipelago have been traced to the Paleolithic, around 38–39,000 years ago. The Jōmon period, named after its cord-marked pottery, was followed by the Yayoi period in the first millennium BC when new inventions were introduced from Asia. During this period, the first known written reference to Japan was recorded in the Chinese Book of Han in the first century AD.

Around the 3rd century BC, the Yayoi people from the continent immigrated to the Japanese archipelago and introduced iron technology and agricultural civilization. Because they had an agricultural civilization, the population of the Yayoi began to grow rapidly and ultimately overwhelmed the Jōmon people, natives of the Japanese archipelago who were hunter-gatherers.Between the 4th and 9th centuries, Japan's many kingdoms and tribes were gradually unified under a centralized government, nominally controlled by the Emperor of Japan. The imperial dynasty established at this time continues to this day, albeit in an almost entirely ceremonial role. In 794, a new imperial capital was established at Heian-kyō (modern Kyoto), marking the beginning of the Heian period, which lasted until 1185. The Heian period is considered a golden age of classical Japanese culture. Japanese religious life from this time and onwards was a mix of native Shinto practices and Buddhism.

The Heian period (平安時代, Heian jidai) is the last division of classical Japanese history, running from 794 to 1185. It followed the Nara period, beginning when the 50th emperor, Emperor Kammu, moved the capital of Japan to Heian-kyō (modern Kyoto). Heian (平安) means 'peace' in Japanese. It is a period in Japanese history when the Chinese influences were in decline and the national culture matured. The Heian period is also considered the peak of the Japanese imperial court, noted for its art, especially poetry and literature. Two syllabaries unique to Japan, katakana and hiragana, emerged during this time. This gave rise to Japan's famous vernacular literature, with many of its texts written by court ladies who were not as educated in Chinese as their male counterparts.

Although the Imperial House of Japan had power on the surface, the real power was in the hands of the Fujiwara clan, a powerful aristocratic family who had intermarried with the imperial family; most Emperors of the Heian era had mothers from the Fujiwara family. The economy mostly existed through barter and trade due to the lack of a national currency, while the shōen system encouraged the growth of aristocratic estates that began gradually asserting their independence from Imperial control. Despite a lack of serious warfare or domestic strife during the Heian era, crime and banditry were widespread as the Emperors failed to police the country effectively.

Minamoto (源; Japanese pronunciation: [mʲi.na.mo.to]) was a noble surname bestowed by the Emperors of Japan upon members of the imperial family who were excluded from the line of succession and demoted into the ranks of the nobility since 814. Several noble lines were bestowed the surname, the most notable of which was the Seiwa Genji, whose descendants established the Kamakura and Ashikaga shogunates following the Heian era. The Minamoto was one of the four great clans that dominated Japanese politics during the Heian period in Japanese history—the other three were the Fujiwara, the Taira, and the Tachibana.

In the late Heian period, Minamoto rivalry with the Taira culminated in the Genpei War (1180–1185 AD). The Minamoto emerged victorious and established Japan's first shogunate in Kamakura under Minamoto no Yoritomo, who appointed himself as shōgun in 1192, ushering in the Kamakura period (1192–1333 AD) of Japanese history. The name "Genpei" comes from alternate readings of the kanji "Minamoto" (源 Gen) and "Taira" (平 Hei).