The Legend of Takeiwatatsu-no-Mikoto of Aso

The Legend of Takeiwatatsu-no-Mikoto of Aso is a foundational myth concerning Takeiwatatsu-no-Mikoto, the opening deity of Mount Aso and the Aso caldera. According to tradition, Takeiwatatsu-no-Mikoto was a grandson of Emperor Jinmu. Standing on the outer rim of the caldera at a place called Tateno, he is said to have kicked through the lake that then occupied the depression, releasing its waters to the sea and revealing a vast plain. Upon this plain, fields and paddies were established, and Takeiwatatsu-no-Mikoto became the ancestor of the Aso kuni-no-miyatsuko (provincial governor of antiquity).

Takeiwatatsu-no-Mikoto is venerated at Aso Shrine together with his consort Asotsuhi-me-no-Mikoto and their son Hayamikatamaのno-Mikoto, forming the core of the Twelve Deities of Aso, a central focus of worship to the present day.

The narrative core divides into three principal scenes: the breaching of the outer rim at Tateno; the cascade of water and the appearance of the plain; and the establishment of cultivation and ritual worship. From the medieval period onward, the legend was systematised as the ancestral narrative of the Aso clan, heads of the Aso shrine, and became a representative example of ancient foundational legends in central Kyushu. It is also positioned as an origin narrative for wet-rice agriculture at the foot of a volcanic mountain.

The primary site of tradition is Aso Shrine (Aso Jinja) in Miyadji, Ichinomiya-machi, Aso City, Kumamoto—the ichi-no-miya (principal shrine) of the former Higo Province. The site of the breaching legend lies in the Tateno gorge on the border between Aso City and Minami-Aso Village, where the landscape features such as Sugaruga Waterfall still carry the legend. Kokuzo Shrine (Kokuzo Jinja) in Teno, Ichinomiya-machi, Aso City, enshrines Takeiwatatsu-no-Mikoto's son and together with Aso Shrine forms the ritual centre of the Aso mythological region.

The *Sendai Kuji Hongi* (Mononobe-school mythological text) provides the literary foundation in its 'Register of Provincial Governors' section on Aso. The legend is further documented in the *Aso Clan Genealogy* and the medieval *Aso Shrine Founding History* (engi). Though absent from the *Kojiki* and *Nihon Shoki*, Aso Shrine is recorded in the *Nihon Sandai Jitsuroku* and the *Engishiki* Register of Shrines.