Hyakumanben Nenbutsu (百万遍念仏)
Hyakumanben Nenbutsu is to repeat nenbutsu (Buddhist invocation) for a million times for the purposes of one's own birth in the Pure Land, ceremony as a memorial, and other variety of prayer.
Originally it is said that an objective may be achieved if one repeats nenbutsu for a million times in seven (or ten) days. There is also an idea that kudoku (merit) of nenbutsu of other people can be interchanged among several people when they pray nenbutsu simultaneously in the same words (for example, if ten people repeat nenbutsu for a hundred thousands times it will have the equal effect as a million times of nenbutsu by one person (10 x 100,000 =1,000,000)). See Yuzu Nenbutsu. In some cases this is done by rubbing big juzu (beadroll) together to count the number while repeating nenbutsu (when done by several people they need to have the same juzu). The juzu which is used in such a case is sometimes called Hyakumanben Juzu.
The first person who related Hyakumanben Nenbutsu and gokuraku ojo (peaceful death) is said to be Kasai of Tang (according to "Jodo-ron" (the Pure Land Treatise written by Kasai)). It was introduced into Japan in the Heian period, and became widespread along with popularization of the Jodo (Pure Land) sect. In 1331, a priest called Zena (Jodo sect) completed Hyakumanben Nenbutsu in seven days by command of Emperor Godaigo to control an epidemic and succeeded in ending it. The jigo (temple name) called 'Hyakumanben,' which is a byname of Chion-ji Temple where he lived, is the title given to a Buddhist temple, as an award at that time. From Muromachi period to Sengoku period (period of warring states) (Japan), Hyakumanben Nenbutsu spread from Imperial Court to rural villages, and it was a rule in the Imperial Court to do Hyakumanben Nenbutsu on 16th of January, May, and September.
Imperial Prince Fushiminomiya Sadafusa in his diary "Kanmon Nikki" wrote the purpose of Hyakumanben Nenbutsu to be plainly as 'ceremony for the past and prayer for the present.'
Today there are cases of Hyakumanben Nenbutsu in the temples and some regions in Japan for the purpose of reposing souls, ceremony as a memorial, fertility, and prevention of disasters.