Sankakuji is famous for its 300- to 400-year-old cherry trees, which still bloom every spring. The poem, "This is why I climbed up the mountain, Cherry blossoms" was written when Kobayashi Issa, a haiku poet of the Edo period, visited here in 1795. This is the last temple in Iyo (Ehime). The temple is located at an elevation of about 360 meters on a quiet hillside of Hiraishiyama.

According to legend, Gyoki founded Sankakuji by order of Emperor Shomu (reigned 724-749) to emulate and embody the Pure Land of Maitreya. In 815 Kobo Daishi visited the temple. He carved and enshrined the principal image of Juichimen Kannon Bosatsu (Eleven-faced Bodhisattva Who Hears the Sounds of the World). He also carved a statue of Fudo Myōō (Immovable Wisdom King). He built a triangular altar and conducted a Goma fire ritual for 21 days, praying for the safety of the nation and the welfare of all people. The remains of this altar still exist as an island in the Misumi no Ike (Triangular Pond) between the Kuri and the Yakushido. This is also the origin of the temple's name. Emperor Saga (reigned 809-823) was deeply devoted to this temple. He granted the temple extensive land holdings. He ordered the construction of seven main buildings and made it a very prosperous temple. However, the temple was damaged by the forces of Chosokabe Motochika during the Tensho era (1573-1592), and some of the buildings were burnt down. The present Hondo was rebuilt in 1849 and restored in 1971.

The principal image has long been revered as a Kannon Bosatsu for good luck and protection from bad luck, and also for safe delivery. Visitors are given a prayer charm and a belly band. Also, it is said that if a couple with no child receive a ladle and have a meal together, they will have a child. After having a baby, they revisit the temple with a new ladle and donate that ladle to give thanks for the blessing of a child.

The pond is more than 10 meters in circumference. There is a small hall enshrining Benzaiten (Goddess of Wealth and Good Fortune) on the triangular island in the pond.