Four villages in Taishi (Aso, Shimo-aso, Tatsuoka, and Yatabe) would depend on the "Iwa-zeki" dam on the Hayashida River for water to grow rice. However, water was scarce in the Hayashida and those villages would often fall short of water after a spell of dry weather.
Fortunately, people in those villages had another dam called "Yoko-zeki" which let water from the nearby Ibo River into the Hayashida. They used the Yoko-zeki dam to make up for the shortage. People in Ishi-umi district, south of the Iwa-zeki dam, also counted on the Yoko-zeki for water.
So in times of drought, villages would fight against each other for water.
It happened at one of those days' nights.
People from another village Iwamii tried to cut down Yoko-zeki after Aso villagers dammed the water stream. The four villages held an emergency meeting, when Yajihei, one of the villagers sneaked out.
"We can't live without water. I will risk my life to protect our water! Try breaking this dam if you can!"
Yajihei laid himself on the dam and never moved an inch. The Iwamii people was also fighting for water, and assaulted Yajihei with spades and hoes in their hands.
At last, Yajihei was killed.
The villages were in such an uproar.
After the incident, the four villages made a pact with Hiroyama village in Tatsuno and they have agreed that they would share Yoko-zeki water forever.

Local map of TAISHI

Historical and Friendly Town TAISHI