Boro was put, as a separate structure, on Yagura of Irimoya-zukuri, so even if the ground surface under Shoju was distorted, the above tiers on top of it were able to be maintained rectangular.
入母屋造の櫓の上に望楼を別構造で載せているので、初重平面が歪んでいても、上重の矩形は整えることができる。