Joyo (958 - 1047) was a Shingon sect Buddhist monk during the latter half of the Heian period. He was also called Kishin shonin and Jikei shonin. His secular surname was Kawai. He came from Katsuragigun in Yamato Province.
He entered Kofuku-ji Temple at the age of 13 and studied the Hosso sect of Buddhism. Later, he received the ritual of consecration of the Esoteric Buddhism by Shingo, the founder of Kojima-ryu. He had deep faith in Hokke-kyo Sutra (the Lotus Sutra) and was an upholder of the Sutra.
It is said that he prayed to Buddha for the happiness for the dead parents, which is called 'Kishin,' recited the Lotus Sutra, and always carried the Sutra, which is called 'Jikyo.'
He visited Hasedera Temple in Yamato to find out whereabouts of his dead parents' body, and received a message from the statue of Goddess of Mercy to go up Mt. Koya. Those days, Mt. Koya was devastated by conflicts with Toji Temple, fire caused by thunderbolt, and the like. Joyo worked for restoring Mt. Koya, living in the mountain by using his own means for protecting against the cold. Meisan was his disciple.
In the inner sanctuary of Mt. Koya, there is a light called 'Kishinto' or also known as 'Poor woman's lamp' that is said to be offered to Buddha by Joyo and has never been gone out to date.