On the Hojo side, Ujimasa arrived at a fort in Mt. Mifune (Kimitsu City), a low mountain in eastern Kazusa Province, to counterattack the Satomi army, while a navy of the Hojo clan was carefully watching Sanuki-jo Castle located in the opposite side of the fort.
氏政はこれを撃退しようと上総東部の低山である三舟山（君津市）に着陣し、水軍もこの砦と向かい合う佐貫城を窺った。