A long time ago, a fisherman from Togitsu Beach caught a great amount of mackerels and decided to go to Nagasaki to sell them. When the fisherman was about to pass under this rock, he thought: 'This rock might fall any moment, so I shall wait until it falls'. He waited for a while. And as he waited, the mackerels slowly began to rot. The name 'Mackerel Rotten Rock' comes from this story.
This rock is of hornblende andesitic volcanic propylite. Appearing at any moment to fall, the rock changes its appearance in every season. Today, incidentally, the rock is fixed in concrete, so it will never fall.