Hirotsugu's cause was supported by discontented farmers, local district chiefs and members of the Hayato minority of southern Kyushu; he also tried to secure support from the Korean kingdom of Silla.
Penyebab Hirotsugu didukung oleh petani yang tidak puas, kepala distrik lokal dan anggota minoritas Hayato di Kyushu selatan, dia juga mencoba mendapatkan dukungan dari kerajaan Korea, Silla.