was a Buddhist monk and sà Âhei, abbot of Hà Âzà Âin temple, and guardian of all the temples of Nara. In the 1560s he founded Hà Âzà Âin-ryà «, a school which taught the art of the spear, also known as Sà Âjutsu.
In'ei was born in the first year of Daiei (1521) as the second son of Nakamikado Tajima Inei who was a warrior monk of the Kà Âfuku-ji. In'ei was a monk of Kà Âfuku-ji Temple in Nara, Japan. He adored martial arts and trained in the sword martial arts of Nen-ryà « under Toda Yosaemon and Tenshin Shà Âden Katori Shintà Â-ryà « under Izasa Ienao. At the same time, he was coached and mentored by , a master of the spear. Under this master's guidance, In'ei honed his spearmanship. According to legends, at dawn of the 12th day of the first month of 22nd year of Tenbun (1553) the 33 year old In'ei was initiated to two secret techniques by Moritada, thought to be the incarnation of Marishi-Ten. In'ei was noted for having arranged the meeting between Kamiizumi Nobutsuna and Yagyà « Munetoshi, being the catalyst for the creation of Yagyà « Shinkage-ryà «.
It is said that one evening, on seeing the reflection of the crescent moon shining on Sarusawa pond in Kà Âfuku-ji, he was inspired to create a spear with a cross-shaped spearhead. He imagined this style of spear would be more effective in fighting. With this new type of spear (known as ), he founded the Hà Âzà Âin-ryà «, based on the teachings of the Shintà Âryà « and the Shinkageryà «.
The development of the Sà Âjutsu of Hà Âzà Âin-ryà « was very successful, until in 1585 Hashiba Hidenaga became lord of Kà Âriyama castle and ordered the temples and Shintà  shrines as well as the ordinary people of the province of Yamato to surrender all weapons. The pressure led to an abandonment of martial arts training in temples and shrines. In 1586 the highest Buddhist title of Hà Âin was bestowed on the 75 year old In'ei. At this time he was requested by Konparu Dayà « Yasuteru to instruct his son Shichirà  Ujikatsu. Because of Konparu's reputation and influence (even on Tokugawa Ieyasu), at the age of 75 revived the Sà Âjutsu training. From then on the number of his disciples increased in a way that people said "the number of those training in this art not only fills a platoon but fills a whole army". In 1604, young Miyamoto Musashi immediately went to Nara and visited the 84 years old In'ei. Due to the old age of the first headmaster of the Hà Âzà Âin-ryà « and due to the youth of his successor (Inshun was only 16) the man who met Musashi's challenge was Okuzà Âin Dà Âei. The legend of Musashi and his visit increased the fame of the school, often mentioned in the stories about Musashi, from Eiji Yoshikawa's novel Musashi to the manga Vagabond.
One year prior to his death (in 1607) In'ei forbade sà Âjutsu training. This should have led to the extinction of at least the monastery line of the school. However, after In'ei's death, his nephew, Hà Âzà Âin Inshun restarted his trainings and lifted the order. Inshun continued the monastery line and further trained his disciples who became masters of the secular line, still alive today. In'ei and his successors (including Inshun) are buried in the graveyard of the temple Byakugà Âji in Nara, where modern Hozoinryu members still venerate them and care for the graves. The school also cares for other memorials, Marishiten boulder (embodiment of the deity Marishiten from the Hà Âzà Âin temple to which In'ei prayed), and the memorial stone on the grounds of the Hà Âzà Âin.