The Twelve Kingdoms Wiki

Kaidou Spring (海桐, sea paulownia) is one of the large springs located at Houro Palace on Mt. Hou.[1] The water comes from a deep hollow in the stone wall.

It is named after the sea paulownia (kaidou) tree that hangs over the spring. The orange and white petals from the flowering tree often fall in the spring and create a lingering fragrance in the water. It makes for a fine purifying libation for the statue of the Consort located in Houro Palace.

In the English translation of the novels, the spring is called the Tobira Spring and the flowering tree is called a tobira.[2]