This is a Soto Zen temple founded in 1625 (the 2nd year of the Kaei era). It is the only temple that escaped destruction by fire during the Hakodate War and is designated as a National Important Cultural Property. To the east of the main hall is the kuri (temple kitchen and living quarters), and to the west is the Ryūjin-dō Hall, which enshrines Ryūjin, the dragon god who governs the safety of maritime navigation.

Additionally, the temple grounds feature the 'Ezo Kasumi Zakura,' one of the three great cherry trees of Matsumae. Dr. Misao Tatewaki, a former professor at Hokkaido University, named the Kasumi Zakura of Ryūun-in. As its name suggests, it is a beautiful tree with very pale crimson blossoms. White-flowered dandelions, which are rare in Hokkaido, can also be seen.