Kaminoi is a well in Hyugadomari on Onyu Island, in Saiki Bay, Oita Prefecture. The well is submerged at high tide, but it is a spring of clear water.
  
Jinmu Emperor stopped at Mimitsu Port in Hyuga during his anabasis to the east. He asked the people there for water but they complained of a shortage of water on the island. Then, the Emperor struck his bow in the ground and said 'Come out, water!'. Surprisingly, clear water began to gush out. This is the origin of the Kaminoi well.

The people of Onyu Island appreciated the water and made a fire tower on the shore to see off the Emperor's ship in the night. This is said to be the origin of the Onyu Island Tondo Fire Festival. This festival is still held every January to pray for everyone's sound health. Torches, over 10m high, are set in the ground and their fierce flames give off strong light making a magnificent sight.