In 1340 when the Northern Court side sent KO no Morofuyu to govern Kanto region, Chikafusa, who was abandoned by the Oda clan, entered Munesuke SEKI's Seki Castle (Chikusei City, Ibaraki Prefecture) to fight against them together with the Southern Court's forces including the Shimotsuma clan in Daiho Castle (Shimotsuma City, Ibaraki Prefecture) and the Isa clan (Hitachi Province) in Isa Castle (Chikusei City, Ibaraki Prefecture).
1340年（興国元年/暦応3年）、北朝方が高師冬を関東統治のために派遣すると、小田氏に見限られた親房は関宗祐の関城（茨城県筑西市）に入り、大宝城（茨城県下妻市）の下妻氏、伊佐城（茨城県筑西市）の伊佐氏(常陸国)など常陸西部の南朝勢力とともに対抗する。