After the Bunei War, Morimune left the capital and went to Kyushu as Shugodai (deputy of a military governor) of Higo Province where his father, Yasumori assumed the position as Shugo (a provincial military governor) in 1276, to prepare for another invasion by Yuan (Dynasty).
文永の役の後、再度の元(王朝)襲来に備えて建治2年（1276年）に父泰盛が守護となった肥後国の守護代として盛宗が九州に下向した。