According to "Kansei Choshu Shokafu", he broke into the castle from the backdoor (on the north side) but faced a violent resistance of the besieged force, so he infiltrated Mizunotekuruwa (a compound of a castle in charge of drawing water) with miners to cause an inner disturbance, then he captured the castle.
「寛政重修諸家譜」によれば、吉政は搦手（北側)から攻め込み、篭城軍の抵抗が激しいので、水ノ手郭に金堀を潜入させ内部を攪乱、落城させることに成功したとある。