This bulwark was built on the beach stretching from Nagatare Mountain to Imayama Mountain, partly financed by the lord of Buzen province in Edo period. Today, the Government-designated areas are in front of Nagatare Kaisuiyokujo and at the bottom of Imayama Mountain. A historical report tells in an ancient document that Narutomi clan, the local clan of Edo period based in Yoshitomi-mura village of Chikujo-gun, was in charge of the construction and finished it in 1303 and it suggests that the construction went on and the nation was kept under a warned status against Mongolians after the Koan Invasion of 1281.