Abdication of the throne (譲位)
Abdication of the throne means that a person with the position of a monarch, such as emperor and king, transfers the position to a successor. In particular, it is succession of the position by heredity. Succession to the throne in this fashion is called juzen (accession to the throne as a result of the monarch's abdication) in East-Asian countries where Chinese characters are used.
The transfer of a position from a powerful person, including a monarch, to another person who he considers is appropriate for the position because he is capable, regardless of heredity or predetermined regulations or customs of succession of a position, is not an abdication of the throne, but jozen (peaceful transfer of power). If a person succeeds the position without the intension of a predecessor, it is not called an abdication of the throne, either.
Abdication of the throne may be considered as representation of the intension of a monarch. For example, Emperor Gomizunoo in the Edo period was unable to endure the deeds of the Edo bakufu which eroded the authority of the emperor, like the Shie Incident (the great conflict between the shogunate and the Imperial Court), and abdicated the throne to an infant Princess Okiko (later Emperor Meisho). This abdication is regarded as a protest from the emperor against the bakufu. Normally, retired emperors had the honorary title of Daijo Tenno (or Joko). Some retired emperors acceded to the throne again (choso [a second accession to the imperial throne]).
However, it is not enough for a monarch to expresses his will to actually carry out the abdication of the throne. Since it required enormous expenses to carry out an abdication ceremony and build a court for the retired emperor, he could not abdicate the throne if the imperial court could not bear the cost. The three emperors (Emperor Gotsuchimikado, Emperor Gokashiwabara, and Emperor Gonara) in the Sengoku period (period of warring states) (Japan), between Emperor Gohanazono who carried out his abdication ceremony in support of the Muromachi bakufu and Emperor Ogimachi who carried out his ceremony in support of the Toyotomi regime, died on the throne.
The abdication of the throne is not permitted in Japan in modern times under the Constitution of the Empire of Japan or the Constitution of Japan. Article 10 of the Former Imperial House Law established in 1889 stipulates, 'When the emperor dies, the Crown Prince ascends the throne and inherits his jingi [the sacred treasures]', which specifies that the crown prince takes the throne when the emperor dies, and article 4 of the Imperial House Law established in 1947 in Japan under occupation also specifies, 'When the emperor dies, the Crown Prince ascends the throne immediately', indicating that the crown prince takes the throne only when the emperor dies, like the Former Imperial House Law. The Former Imperial House Law specifies the order of succession to the Imperial Throne clearly, and the article 2 of the current Imperial House Law stipulates the order of succession to the Imperial Throne and the article 3 specifies the changes of the order, so the emperor cannot appoint his successor on his own free will.