According to the ancient myths, Emperor Chuai and his consort Jingu travelled to Kyushu to fight the Kumaso people of southern Kyushu. Jingu was known as a shamaness and she received a message from the kami that they should attack and subdue the countries on the Korean Peninsula. Chuai scoffed at the idea and was promptly killed by the kami. Jingu took over and organized a military invasion of the peninsula. She was pregnant with the child of Chuai and in order to stop the child being born before she returned she placed 2 smooth, round stones "in her loins".
Jingu was gone 3 years and when she arrived back she safely gave birth to the child who would become Emperor Ojin. The name of the place she gave birth was changed to Umi, and now a Hachimangu shrine stands at the place.
Behind Umi Hachimangu is a large container filled with stones, koyasunoishi, safe birth stones. A woman who prays at the shrine for a safe birth for her child will take oe of the stones home with her. Upon the safe birth of the child the woman must then find another stone and write the new childs name and birthdate on it before returning both stones to the shrine.