On the night of September 3, 1918, when riots against the rising price of rice spread all over Japan,
a great dynamite explosion was caused by some people on the refuse heap of the No.4 pit of the Kamimio Coal Pit.
This riot by pit workers had a great effect on the treatment of miners at the neighboring San-nai Coal Pit.
The pit announced the next day that the amount of wages of their miners rose to almost twice as much as those before.
The miners at the pit were reportedly very pleased to have profited from the situation
which had changed suddenly due to the confusion at the Kamimio Coal Pit.