It was built by Prince Shotoku in the first year of the reign of Empress Suiko (593) as "Seiyakuin," one of the four temples of Shitennoji. Seiyakuin was a welfare facility established in accordance with Buddhist teachings, cultivating medicinal herbs and providing them to people according to their illness. Later, Prince Shotoku lectured people on the Sutra of the Victory over Mantra and enshrined a statue of Lady Srimala (Lady Victory over Mantra) in the main hall, so the temple came to be called "Shomanin." In addition, the main hall enshrines Aizen Myoo, who is famous for finding a good match and marital harmony, as the principal image, so the temple is also known as "Aizen-do." In addition to the Tahoto Pagoda (a national important cultural property), a masterpiece of the Momoyama period rebuilt by Toyotomi Hideyoshi, the temple also has "Aizen no miraculous water," which is said to make love come true when you drink it, and is popular among young women. The Aizen Festival, famous as one of Osaka's three major summer festivals, is held every year on June 30th and July 1st and 2nd.