The "hon-maru" residence, which was located to the north of the foundation of the "dai-tenshu" (large donjon), served as a domicile for lords until the second lord, Kuroda Tadayuki, built a new residence in the "san-no-maru". In the "hon-maru" residence, there was a 56 tatami-mat (109 sq.m. in Chikuzen) audience chamber and the Shaka-no-ma (Buddha Room) where Iken-kai (regular meetings in which principal retainers were permitted to freely speak their opinions whether they agreed with the lord's position or opinion or not) were held.