Banding together with the Ikkoshu sect in the fight against the then powerful Nobunaga ODA, Imai-go was turned into a fortress whereby a moat as well as earthen walls were built around the town and, to guard the westernmost of that town, a castle-like structure (the present Imanishi-ke Jutaku site) equipped with various appropriate features such as turret was constructed.
一向宗と結んで、時の権力者織田信長と闘うために街の周囲に環濠土塁をうがち、西から今井を守るべく櫓などを備えた城構え（現今西家住宅地）を築き城塞都市化している。