Jinmu tenno sai (Emperor Jinmu Ceremony) (神武天皇祭)

Jinmu tenno sai (Emperor Jinmu Ceremony) refers to the ceremony of the Imperial Household to honor Emperor Jinmu. It was one of the public holidays in the prewar period. Today, it is performed on April 3 (based on the new calendar). It is performed in commemoration of the first emperor, Emperor Jinmu. The date of April 3 is evaluated by converting the date of March 11, AD 586 (in the lunar calendar), which is said to be the day of the demise of the Emperor, into the Gregorian calendar. The ceremony is performed in Kyuchu sanden (the Three Shrines in the Imperial Court) and the Mausoleum of Emperor Jinmu.

Jinmu tenno-sai Festival commenced in the generation of Emperor Komei in the closing days of the Edo bakufu (Japanese feudal government headed by a shogun), and it was regulated under the 'Shiji Saiten Teisoku' (the Regulations of Seasonal Ceremonies), which was defined in September 1871. After that, it was given legal force under the 'Koshitsu Saishi Rei' (the Ordinance of Imperial Household Religious Rites) in 1908. It was officially abolished in 1947, but it still continues as a private ceremony of the Imperial Household.

Although it is just one of the religious services for the ancestors of the Imperial Household, Emperor Jinmu is treated differently from the other successive emperors. A religious service is performed for four previous emperors (going back four generations from the current emperor) on the anniversary of their death each year, while a religious service is performed for other emperors only on Shiki nen sai: 3 years, 5 years, 10 years, 20 years, 30 years, 40 years, 50 years, subsequently 100 years after the death of an emperor. However, the religious service for Emperor Jinmu is performed every year as he is the first ancestor of the Imperial line. Therefore it is called Jinmu tenno-sai instead of Jinmu tenno-reisai, although the term "reisai" (an annual ceremony) is used for the festivals for the other emperors.

On the day of Jinmu tenno-sai Festival, a ceremony is performed at the Korei-den (the Imperial Ancestors' Shrine), and an imperial messenger is sent to the Mausoleum of Emperor Jinmu to offer heihaku (Shinto offerings such as cloth, paper, and rope). Under the old system, it was speculated that the emperor himself visits the mausoleum of Emperor Jinmu on shiki nen sai for worshipping.

Rites and festivals are performed at some shrines across the country, mainly at the shrines that honor Emperor Jinmu such as Kashihara-jingu Shrine and Miyazaki-jingu Shrine.