Makabe Harumoto served as a bushō during the early Sengoku period.  Harumoto was a kokujin, or provincial landowner, and served as the lord of Makabe Castle in the Makabe District of Hitachi Province.

Harumoto was born as the son of Makabe Hisamoto.  After Hisamoto entered the priesthood and adopted the monk’s name of Shinrakusai, Harumoto succeeded him as head of the clan, but Hisamoto continued to hold on to power.  Following the death of Hisamoto in 1507, Harumoto began to fully engage as the head of the clan.

According to one theory, Harumoto may have been married to the older sister of Oda Masaharu, but there is a lack of authenticated accounts to support the view.  It is surmised that Harumoto received one of the characters in his name from Masaharu’s father, Oda Shigeharu.

In connection with internal struggles in the family of the Koga kubō during the Eishō Conflict (1506 to 1518), Harumoto initially aligned with Ashikaga Masauji, but, around 1514, he solicited Oda Masaharu and abandoned Masauji in favor of Ashikaga Takamoto.  Nevertheless, cordial relations between Harumoto and Masauji continued after this time, so the switch in support of Takamoto may have been at the initiative of Harumoto’s son, Makabe Iemoto, which event may have accompanied a change in the headship of the Makabe clan.