Ninmyō ascended to the throne following the abdication of his uncle, Emperor Junna.
6 January 823 (Kōnin 10, 4th month, 19th day): Received the title of Crown Prince at the age of 14.
22 March 833 (Tenchō 10, 28th day of the 2nd month): In the 10th year of Emperor Junna's reign, the emperor abdicated; and the succession (senso) was received by his adopted son. Masara-shinnō was the natural son of Emperor Saga, and therefore would have been Junna's nephew. Shortly thereafter, Emperor Ninmyo is said to have acceded to the throne (sokui).
Shortly after Ninmyo was enthroned, he designated an heir. He named Prince Tsunesada, a son of former Emperor Junna, as the crown prince.
835 (Jōwa 2): Kūkai (known posthumously as Kōbō-Daishi) died. This monk, scholar, poet, and artist had been the founder of the Shingon or "True Word" school of Buddhism.
842: Following a coup d'état called the Jōwa Incident, Tsunesada the crown prince was replaced with Ninmyō's first son, Prince Michiyasu (later Emperor Montoku) whose mother was the Empress Fujiwara no Junshi, a daughter of sadaijinFujiwara no Fuyutsugu. It is supposed that this was the result of political intrigue planned by Ninmyō and Fujiwara no Yoshifusa. The first of what would become a powerful line of Fujiwara regents, Yoshifusa had numerous family ties to the imperial court; he was Ninmyō's brother in law (by virtue of his sister who became Ninmyō's consort), the second son of sadaijin Fuyutsugu, and uncle to the new crown prince.
6 May 850 (Kashō 3, 21st day of the 3rd month): Emperor Ninmyō died at the age of 41. He was sometimes posthumously referred to as "the Emperor of Fukakusa", because that was the name given to his tomb.
Eras of Ninmyō's reign
The years of Ninmyō's reign are more specifically identified by more than one era name (nengō).
In general, this elite group included only three to four men at a time. These were hereditary courtiers whose experience and background would have brought them to the pinnacle of a life's career. During Ninmyō's reign, this apex of the Daijō-kan included:
^Spelling note: A modified Hepburn romanization system for Japanese words is used throughout Western publications in a range of languages including English. Unlike the standard system, the "n" is maintained even when followed by "homorganic consonants" (e.g., shinbun, not shimbun).