A monk named Zenkai had once stopped by Yabakei during a journey, and felt great pain upon seeing the numerous people falling to their death from the river bridge. In Kyoho 2 (1735 A.D.), he took it upon himself to dig through the stone walls. Zenkai managed to collect some money from alms, and dug together with the masons he hired with just a hammer and a chisel for 30 years until the 1122 foot (342 m) long tunnel was finally complete in the first year of the Showa era (1764 A.D.).