With Hoi County as the main battle field, he fought with the Imagawa clan that delayed in taking actions for Mikawa Province, and then by 1566, he conquered the eastern Mikawa area and the Oku-Mikawa area (the northern part of Mikawa Province), unifying Mikawa Province.
三河国への対応に遅れる今川氏との間で、宝飯郡を主戦場とした攻防戦を繰り広げた後、永禄9年（1566年）までには東三河・奥三河（三河国北部）を平定し、三河国を統一した。